Large business groups face the risk of the entire group becoming insolvent due to excessive cross-debt guarantees among affiliates. Therefore, starting in 1995, the government required listed corporations to make comprehensive public disclosures detailing the circumstances of debt guarantees when deciding on guarantees amounting to 10% or more of their capital, thereby seeking to protect stock investors. The purpose of this paper is to analyze the impact of debt guarantee disclosures on the abnormal returns of both guarantor and guaranteed company stocks, as well as the determinants of those abnormal returns. According to the research findings, debt guarantee disclosures cause stock price declines for guarantor and guaranteed companies that do not belong to the top 30 large business groups; in contrast, they have no significant effect on the stock prices of guarantor and guaranteed companies belonging to the top 30 large business groups. Cross-sectional regression analysis of abnormal returns and their determinants revealed that the variables suggested by the leverage signaling model are statistically significant in explaining differences in abnormal returns of guarantor company stocks. On the other hand, differences in abnormal returns of guaranteed company stocks were not statistically significantly explained by the variables suggested by the leverage signaling model and the option pricing model. However, the dummy variable indicating whether the guaranteed company belongs to the top 30 large business groups and the debt ratio of the guaranteed company were found to be significant in explaining differences in abnormal returns of guaranteed company stocks.