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 a carboxylic acid compound 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 neonicotinoid compounds selected from the group (A) consisting of imidacloprid, clothianidin, thiamethoxiam, dinotefuran, acetamiprid, thiacloprid and nitenpyram, shows an excellent controlling efficacy on harmful arthropods.
