Provided is an insecticidal composition that has a wide insecticidal spectrum, is highly active, enables a reduction in the amount of an active ingredient to be applied, and has a long-lasting effect. Also provided is an insect pest control method. The insecticidal composition contains, as active ingredients, (A) at least one organic phosphorus compound selected from the group consisting of fosthiazate, imicyafos and cadusafos, and (B) fluensulfone. The insect pest control method applies respective effective amounts of (A) and (B).本發明係提供具有廣泛的殺害蟲光譜，活性高，有效成分之施用量可低減，且持續效果長的殺害蟲性組成物，及害蟲之防除方法。本發明係一種殺害蟲性組成物，其係含有(A)由噻唑膦(fosthiazate)、氰胺雜環類有機物(imicyafos)及硫線磷(cadusafos)所成之群中選出的至少1種之有機磷系化合物，與(B)氟噻蟲碸(fluensulfone)作為有效成分，以及一種害蟲之防除方法，其係施用上述(A)及(B)之各有效量。
