The Korean government has introduced land policy reform measures recently, in order to stabilize the circulating system of land, without a parent law involving effective land use. The measures aim to change the pattern of land market rather than the pattern of land use. Expecially, the excessive profits tax on land intends to redistribute the owernership of residential land, and to recapture windfall gains on an accrual basis. However, it may incur secondary gains in macro economics and an unintended reduction of urban land supply in the land market. This paper aims to study empirically the impact caused by the excessive profits tax on land, and to promote urban land supply. Ultimately, this paper can be regarded as an interim report on outcome of research projects which aim to propose a method of urban land supply suitable to an advanced society.