Following the implementation of the “Contract Industry Accounting Transparency Improvement Measures” (hereafter “Improvement Measures”), firms are required to disclose detailed information (completion rates, due from customers for construction work, accumulated impairment losses, etc.) for each individual workplace in the case of contracts that account for 5% or more of the firm’s sales. Therefore, this study examined if investors discriminately interpreted the construction contract information of individual workplaces after the implementation of the Improvement Measures and reflected the same in their decision-making process. Through this, it weighs the usefulness of the reporting amendments following the Improvement Measures. The analysis results show that the larger the accumulated impairment losses of due from customers for construction work in individual workplaces that are nearing completion (over 90% completion rate), the cost of capital in the next period was significantly higher. However, there was no significant relationship between the accumulated impairment losses of due from customers for construction work in individual construction workplaces with completion rates below 90% and the cost of capital in the next period. This is the result of investors estimating that the larger are accumulated impairment losses at individual workplaces that are nearing completion, the higher will be the uncertainty associated with future profit and cash flow. Therefore, they made negative decisions.