Green space potentially promotes positive mental health in people. Consequently, the role of green spaces has become increasingly important because of the new coronavirus disease (COVID-19). While the association between green space and depression was explored during the COVID-19 pandemic, population data on this relationship before and after the pandemic are lacking. Furthermore, how different types of green space impact depression needs clarification. Thus, this study investigated the association between two vegetation types of green spaces(forests and grass) and perceived depression in South Korea before and after COVID-19 using population data. The percentage of forest areas had a significant negative effect on perceived depression before and after COVID-19. However, the percentage of grass areas had no significant effect on the perceived depression. A 1% increase in forest area reduced perceived depression by 16 people per 100,000 people. These findings are expected to contribute towards advancing public mental health and natural environment domains, and forests should be prioritized to capture the mental health needs of citizens.