Recently, transaction of contaminated site is one of major issues of real estate and real estate appraisal industry in Japan.The people have come to demand the appraisal of contaminated site.Since the United States is an advanced country in the valuation of contaminated site, the idea of US becomes reference very much for development of appraisal technique in Japan.The purpose of paper is to introduce the present situation of appraisal for contaminated site in Japan with comparison study between US and Japan.There are three major factors, that is, uncontaminated value, cleanup cost and stigma, to estimate the value of contaminated site.Most difficult problem is how to estimate negative value adjustment caused by stigma.I discuss about these three factors from both theoretical and practical aspects.