The primary goal of this research is to determine the impact of an amendment to the Urban Improvement Act on the duration of redevelopment projects. Basic statistics analysis results reveal an increased redevelopment project period since the amendment, high number of households and tenants of existing houses, and high ratio of general sales and rental of completed houses. Meanwhile, the results of multiple regression analysis, which uses the period from the establishment of the implementation union as a dependent variable, reveal that the amendment increases the project period, and the project period increases if the key interest rate rises and the GDP growth rate is high. With an increased key interest rate, GDP growth rate, and construction investment, the project period decreases. Meanwhile, when the Seoul land price and price index increase, the project period increases. The amendment has improved public interest by increasing the supply of rental housing, but administrative support for the redevelopment of unviable areas must be strengthened to prevent urban polarization.