This paper examines whether the strengthening of regulations actually improves the quality of credit ratings. The empirical analysis is based on September 2013 when the regulation on credit evaluation was transferred to the Capital Market Act. This study examines the effects of strengthening regulations in three aspects. First, after the regulation, it is found that the level of the credit rating itself falls on average. Second, when verifying the change in the accuracy of the credit rating, it is found that the type II error, that is, the false warning of the credit rating company's corporate credit has increased. Third, when examining the information effect of credit rating changes after regulation, no significant difference is found. These results are common to all three credit rating agencies. Taken together, the overall fall in credit ratings was found after the regulation of the Capital Markets Act in 2013, but this had the adverse effect of increasing the second type of error, a false warning of corporate credit. Considering that credit ratings has declined overall, but at the same time, accuracy has declined since regulation, it is difficult to argue that regulation solves the problem of rating inflation. In addition, as a result of comparing the cumulative abnormal return on the announcement date of the credit rating change before and after the regulation, the size of the return decreases in both the downward and upward disclosures. This shows that the strengthening of regulations further reduces the information effect of the credit rating change. This study shows that regulatory changes can affect the quality of capital market information, and also that it is necessary to recognize and prepare for the side effects of regulation.