The present invention provides: a composition for controlling pests comprising, as active ingredients, ethaboxam and avermectin. Also provided is a method for controlling pests which comprises applying effective amounts of ethaboxam and avermectin to a pest, a plant or soil for growing a plant. Further provided is a seed treatment agent comprising, as active ingredients, ethaboxam and avermectin and a plant seed treated with effective amounts of ethaboxam and avermectin.