According to Taiwan's insurance regulations, insurance companies may invest up to 30% of investment asset in real estate; however, a single real estate transaction may not exceed 35% of the insurance company's net worth. In recent years, Taiwan's insurance industry and relevant authority have discussed whether to discard the restriction on the capital utilization ratio in order to give insurance companies more autonomy in investment portfolio. This study investigated Japan's supervision measures regarding investment portfolio of insurance company in real estate investments. Comparison of mechanisms can to provide a reference for similar measures on investment portfolio in Taiwan.