The present invention provides an animal ectoparasite-controlling agent containing as an active ingredient a hydrazide compound represented by the formula (1) wherein R 3 represents a fluorine atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group or a hydrogen atom, R 5 and R 6 are the same or different each other and each represents a methyl group or a hydrogen atom, R 4 represents a C3-C6 cycloalkyl group, which shows excellent controlling effects on animal ectoparasites.