Mercury has attracted great attention as persistent bioaccumulative and toxic substance. Mercury atmospheric emission inventories are indispensable basic data for international management and control of mercury emission. In this study, mercury atmospheric emission in Japan ant its temporal trend were reported. Evaluating the reliability or confidence intervals of emission factors and removal efficiencies for exhaust gas treatment equipments, mercury emission in 2002 was estimated to be 21 to 28 Mg/yr. For 16 years since 1990, mercury emission showed decreasing trend followed by increasing trend. Dry-cell battery manufacturing without mercury contributed to decreasing trend. Rising consumption of coal and increased amount of incinerated sewage sludge contributed to increasing trend of mercury emission. Because of the promotion of sewage sludge incineration treatment and other emerging mercury emission sources, mercury emission would be increased potentially. Exhaust gas treatment equipments that had higher removal efficiency should be applied for effective reduction of mercury emission.