Even though a number of sophisticated methods have been developed as FirmValuation Methods, the stock valuation with PER is still used by those experts of firm valuation and investors. Furthermore, the fact that the low PER of Korea’s major enterprises was mentioned as a representative case of Korea Discount at the time of IFRS adoption also showed that PER had been widely used as a recapitulative and common index. This study has sought out an empirical evidence for the phenomenon of Korea Discount and the opaqueness of accounting information which was discussed at the time of IFRS adoption by analyzing the relationship between the quality of accounting earnings and PER. If the lower quality of accounting earnings causes lower PER, the qualitative properties of accounting information may be considered to be related to PER, which is connected to the argument of the advocates of adopting IFRS that the quality of accounting earnings improved will be reflected to PER. Second, the relation between the quality of accounting earnings and PER after and before IFRS adoption has been compared and analyzed. Then, it was anticipated to be reduced, which was because of principle-based approach and the enhancement of fair value measurement that are key features of IFRS. If it is possible for the principle-based accounting principles after IFRS adoption to reflect an enterprise’s economic achievement and financial status to the accruals, market will not evaluate discriminatively the accounting earnings which are measured as discretionary accrual. That is because the large discretionary accrual, itself, reflects the internal economic substance of an enterprise. The accruals reflects the manager’s discretionary accounting choice, and the discretionary accruals used as a proxy of earnings quality becomes big when there is any discretionary accounting choice. The manager’s discretionary accounting choice may be either a manifestation of opportunistic motivation or means for delivering privately dominated information. If the economic substance can be reflected more basically, IFRS will allowmanagers to have more of discretionary accounting choices. Also, if the process of delivering a manager’s privately dominated information is to be reflected to the information on accounting accruals better, the capital market will not have any reason for underestimating it and, in addition, there will not be significant relation between discretionary accruals and PER. On the other hand, the rule-based accounting principle before the adoption of IFRS is decided by the accounting management method based on the detailed instructions for accounting treatment and bright line method. There will be a great likelihood that the opportunistic accounting treatment is executed by managers in the way of satisfying only the threshold specified at the instructions for accounting treatment regardless of any economic substance of transaction. In the environment of rule-based accounting principle, the accruals from the manager’s discretionary accounting choice will be likely to be the result of earnings management by his opportunistic motivation rather than that from reflection of the manager’s privately dominated information. Accordingly, under the rule-based accounting principle, the markets will devaluate the stocks of the enterprise whose accounting earnings are estimated to be low, in other words, that showing discretionary accruals. Consequently, there will be a closer relation between accounting earnings quality and PER. Since the properties of the information reflected to discretionary accruals is different, there will be a big difference in the market’s evaluation of the accounting earnings calculated through these accruals, that is, there will be the difference of PER. Furthermore, IFRS will require to more information which is to be included on accounting earnings. As the information on fair value measurement and managers’ discretionary choice for various alternatives to accounting treatment is reflected to the process of producing accounting information, there may be the possibility that investors will have more difficulties in interpreting and comparing it than when that information is produced by rule-based accounting principle. The result of empirical analysis, as expected, showed that the higher the quality of accounting earnings represented as a variable of discretionary accruals of the Adjusted Jones Model of Dechow et al.(1995) and accrual quality of Dechow and Dichev(2002), the higher PER is estimated. However, in case of real earnings management where the earnings are managed through managing real transactions, there was not shown any significant relation to PER. The analysis of what difference was made in the relation between PER and discretionary accruals before and after the application of IFRS shows that the relation has become less after its adoption. That is, it means that the size of discretionary accruals has a negative effect on PER but that this kind of phenomenon is becomes significantly weaker after its adoption. Also the variable of accrual quality has the same directivity while its statistical significance is seen to decrease, which indicates that the degree of markets’ discriminative evaluation on the quality of accounting earnings measured as abnormal accruals after its adoption has got lower than that in the environment of previous accounting standards. However, no significant relation could not be found in the case of real earnings management. It is because managers’ privately dominated information was reflected to the abnormal accruals through discretionary accounting choice under K-IFRS or markets were not good at evaluating the large amount of information reflected to the accounting earnings. According to Choi and Kim (2005), if those abnormal accruals are not the outcome of managers’ opportunistic earnings management but play the role of informing investors of the enterprises’ internal private information along with the enforcement of their discretionary accounting choice under the rule-based accounting principle, the negative evaluation in markets on those abnormal accruals will be considerably less than under any previous accounting standards. The findings of this study which has clarified that PER is influenced by the quality of accounting earnings suggest that the properties of accounting information may have some effects on the firm evaluation. Moreover, it is also showing the empirical evidence on what difference in the evaluation of markets on accruals information will be made by the change from accounting environment with rule-based accounting principle to that of principle-based accounting standard. The understanding of what effects those many unique features of IFRS have on markets’ evaluation of accounting information is thought to have an important meaning for establishment and improvement of accounting standards, and that is why the findings from this study are very significant.