The COVID 19 outbreak had a disastrous impact on the global banking sectors. At its lowest point in March 2020, the KOSPI has dropped by arround 33% from its peak earlier in the year. To overcome the crisis, the banking sector needs to analyze the effect of COVID-19 and differences between before and during period. The purpose of this study is to analyze the differences of stock return, how financial performance and macroeconomic indicators affect stock return, and the difference of affect on the stock returns of four prime commercial banks in south Korea before and during COVID-19.