PM10 and PM2.5 in ambient air were collected in Seongbuk-gu area of Seoul for one year, from April 2005 to February 2006, and the concentration of PM-bound mercury was monitored. The annual concentrations of particles were $66.4{pm}43.2{mu}g/m^3;(47.6{pm}19.1{mu}g/m^3-106.1{pm}78.0{mu}g/m^3)$ in PM10 and $37.2{pm}20.4{mu}g/m^3;(28.0{pm}23.4{mu}g/m^3{sim}42.7{pm}21.4{mu}g/m^3)$ in PM2.5, which is about 56% of PM10 concentration. The annual average concentrations of mercury were $0.125{pm}0.078ng/m^3;in;PM10;and;0.141{pm}0.080ng/m^3$ in PM2.5, respectively. In April of Asian dust season in Korea, mercury showed the highest concentration in both PM10 and PM2.5.