Piperazine compound represented by Formula (I), ** Formula ** in which R1 is C1-6 alkyl； R2 is hydroxy, C1-6 alkyl which may have one or more substituents, - (C>； = O) -N (R3) (R4), or - (C>； = O) -OR5； R3 and R4 are the same or different, and each represents hydrogen or C1-6 alkyl that can have one or more substituents, or R3 and R4, taken together with a nitrogen atom to which R3 and R4 are attached, can form a saturated heterocyclic group； R5 is hydrogen or C1-6 alkyl which may have one or more substituents； and n is 1 or 2； or a salt thereof, and in which the term "substituents" means substituents independently selected from the group consisting of halogen, hydroxy, cyano, nitro, alkyl, halogenoalkyl, cycloalkyl, cycloalkyl-alkyl, aralkyl, alkenyl, alkynyl, alkoxy, halogenoalkoxy, cycloalkoxy, cycloalkyl-25 alkoxy, aralkyloxy, alkylthio, cycloalkyl-alkylthio, amino, mono- or dialkylamino, cycloalkyl-alkylamino, acyl, acyloxy, oxo, carboxy, alkoxycarbonyl, aralkyloxycarbonyl, carbamoyl, unsaturated heterocyclic groups, aromatic hydrocarbon and saturated heterocycloxy group； and in these substituents: alkyl or halogenoalkyl is a linear or branched C1-6 alkyl group or a group in which one to all hydrogen atoms of the alkyl group is substituted by halogen； cycloalkyl is a C3-7 cycloalkyl group； cycloalkyl-alkyl is a C1-6 alkyl group substituted with C3-7 cycloalkyl； aralkyl is a linear or branched C1-6 alkyl group substituted with a C6-14 aromatic hydrocarbon group； alkenyl is a C2-6 alkenyl group that contains a carbon-carbon double bond； alkynyl is a C2-6 alkynyl group containing a carbon-carbon triple bond； alkoxy or halogenoalkoxy is a linear or branched C1-6 alkoxy group or the halogen substituted alkoxy group described above； cycloalkoxy is a C3-7 cycloalkoxy group； cycloalkyl-alkoxy is a C1-6 alkoxy group substituted with C3-7 cycloalkyl； alkylthio is a linear or branched C1-6-thio alkyl group； cycloalkyl-alkylthio is a C1-6-thio alkyl group substituted w
