Many countries are computing the Housing Affordability Index (HAI) in order to testify housing purchasing power. However, Korea has never tried to calculate HAI while housing price indexes are constructed and published weekly. This study computes Housing Affordability Index of Korea and testify the usability of leading indicator in the housing finance market. The main results are summarized as follows: First, HAI shows different path from PIR, the existing housing affordability measure in Korea. Second, HAI can cause the housing construction starts and housing loan balance. The findings provide some policy implications. First, we can compute reasonable HAI with available data in Korea housing market. Second, HAI describes better housing price change and housing demand change after Korea Financial Crisis than any other indexes such as PIR. Third, it is necessary to produce HAI and analyze it with PIR in order to improve the market searching ability.