The present invention provides a composition for controlling harmful arthropods having an excellent control efficacy on harmful arthropods. A composition for controlling harmful arthropods comprising an carboxylic acid represented by a formula (I) wherein each of symbols are the same as defined in the Description; or salts thereof and at least one kind of pyrazole compounds selected from the group (A) consisting of chlorantraniliprole, cyantraniliprole and a compound represented by a formula (II), shows an excellent controlling efficacy on harmful arthropods.