​This study analyzed the impact of a price ceiling system on apartment prices in Seoul and three Gyeonggi-do cities using the difference-in-differences method. The sample is divided into speculative and non-speculative areas to account for other policies and regional variations in the policy effect. Results showed that the policy reduced prices in speculative areas post-announcement, with no significant effect in non-speculative areas, confirming heterogeneous policy effects across areas. A dynamic analysis showed the policy's diminishing negative impact on housing prices over time. Additionally, deregulation of the policy increased prices, particularly in speculative areas, exacerbating price imbalances. These findings suggest that the price ceiling system may have unintended consequences, requiring careful implementation to meet policy goals.