Objectives : The purpose of this study is to investigate the correlation between amalgam restorations and urinary mercury levels in children for 1 year. Amalgam restoration has been widely used for over 200 years. But released mercury from amalgam can increase the concentration of mercury in the body. Methods : The subjects were 463 elementary school children. Oral examination, urine sampling, and questionnaire survey were performed at baseline and after 1 year. Results : Amalgam restoration increased the urinary mercury level to $0.55{pm}0.13{mu}g/g$ creatinine. In the regression analysis, variation of urinary mercury excretion were positively associated with amalgam surfaces and fish consumption. Conclusions : Small amount of mercury release from amalgam restoration was closely associated with increasing urinary mercury level.