This study was performed to survey the $SO_2$ level at several underground spaces connected to 5 subway stations (City Hall, Nam, Seoul stations, Hye Hwa and Ulchiro 1 Ga) in Seoul. The period of survey was from July to November, 1997.The results of the study were as follows; 1. The mean concentration of $SO_2$ was $0.057{pm}0.015ppm$ in all subway stations. The highest $SO_2$ level among the five stations was $0.067{pm}0.011 ppm$ at City Hall (P<0.01), and the highest with $0.071{pm}0.013ppm$ at November (P<0.01).2. In underground shopping centers, the mean concentration of $SO_2$ was $0.112{pm}0.059ppm$. 3. The mean concentration of $SO_2$ at evening with 0.057 pp and morning with 0.053 ppm were significantly higher than at noon with 0.043 ppm(P<0.05). 4. The $SO_2$ level of floor at Kang Nam station with 0.044 ppm was significantly higher than that of platform with 0.37 ppm(P<0.01). 5. For the City Hall stations, the line #1 and line #2 subway spaces show significantly different level of $SO_2$, 0.042ppm and 0.033 ppm respectively (P<0.05).