The present invention provides a novel piperidine compound of the formula [I]: wherein Ring A represents an optionally substituted benzene ring, Ring B represents an optionally substituted benzene ring, R.sub.1 represents an optionally substituted alkyl group, an optionally substituted hydroxyl group, etc., or a group of the formula: (a) wherein R.sub.11 and R.sub.12 are the same or different, and each represents hydrogen atom, a substituted carbonyl group, a substituted sulfonyl group, an optionally substituted alkyl group, etc., R.sub.2 represents hydrogen atom, etc., Z represents oxygen atom or a group represented by --N(R.sub.3)--, R.sub.3 represents hydrogen atom or an alkyl group, etc., R.sub.4 represents hydrogen atom or an alkyl group, etc., or a pharmaceutically acceptable salt thereof. ##STR00001##