This invention relates to a piperazine compound represented by Formula (I), wherein R1 is C1-6 alkyl R2 is hydroxy, C1-6 alkyl that may have one or more substituents, -(C=O)-N(R3) (R4), or - (C=0)-OR5 R3 and R4 are the same or different, and each represents hydrogen or C1-6 alkyl that may have one or more substituents, or R3 and R4, taken together with a nitrogen atom to which R3 and R4 are attached, may form a saturated heterocyclic group R5 is hydrogen or C1-6 alkyl that may have one or more substituents and n is 1 or 2 or a salt thereof.