The invention is a method of exterminating a harmful insect with an agricultural and horticultural insecticide containing one or more kinds of compound (A) selected from a specific polyoxyethylene fatty acid ester, a specific polyoxyethylene sorbitan fatty acid ester, a specific (poly)glycerol fatty acid ester, and a specific alkyl saccharide, and a compound (B) of an alcohol having a linear or branched alkyl group having 8 to 14 carbon atoms or a linear or branched alkyl ether having 6 to 12 carbon atoms, provided that an agricultural chemical ingredient of an agricultural chemical is not substantially contained.
