Based on the hedonic pricing method, this paper investigates the effect of air quality on the apartment price in Seoul. The empirical results show that both the structural variables such as years of construction, heating system, and size of apartment complex and accessability variables such as distances to subway station and parks provide statistically significant effects on the price of apartment, Especially, the dendity of sulfurous acid gas (SO_2) and ozone (O_3) in the air, indicating air quality, negatively affect the price of apartment, This implies that as the condition of air quality to become worse, apartment price decreases, Therefore, when the degree of aversion of apartment residents against the air pollution affects the formation of apartment`s market price, the MWPT (Marginal Willingness to Pay) in order to improve the air quality 10% has been estimated as 36,000 ∼ 39,000Won per month.