Animal waste contains some antibiotics administered to livestock. Therefore, when they are applied to agricultural land as compost, the antibiotics are released into the soil environment. This study investigated sulfamethazine (SMZ) sorption and degradation in three types of soil and their behavioral mechanisms. Furthermore, a tracer experiment using SMZ labeled 14C was conducted to obtain the percentage of degradation products of SMZ in gray lowland soil. SMZ was degraded with contact time in andosol and gray lowland soil, whereas little degradation and sorption were observed in brown forest soil. Furthermore, SMZ degradation was suggested to be a contributor, because of the activity of soil microorganisms. Moreover, the soil sorbed some SMZ degradation products, and the others rapidly degraded to CO2.