A piperidine compound represented by a general formula (I) or a salt thereof: wherein, R1 represents a carboxyl group, —C(═O)NR5R6, or an oxadiazolyl group optionally having a C1-C6 alkyl group or a trifluoromethyl group as a substituent； R2 represents a halogen atom or a C1-C6 alkoxy group； R3 represents a phenyl group optionally having 1 to 3 same or different group(s) selected from a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, and a trifluoromethyl group as a substituent； R4 represents a hydrogen atom or a C1-C6 alkyl group； and R5 and R6 are the same or different and each represent a hydrogen atom, a C1-C6 alkyl group, or a C3-C6 cycloalkyl group, or R5 and R6 optionally form a 3 to 6-membered nitrogen-containing saturated heterocyclic group together with a nitrogen atom to which R5 and R6 are bound, are provided.
