The invention provides melanin-concentrating hormone receptor antagonists containing as the active ingredient piperidine derivatives represented by the general formula [I]: [wherein R1 is hydrogen, hydroxyl, lower alkyl, or the like; R2, R3a, R3b, R4a, R4b, R5a, R5b and R6 each stands for hydrogen, halogen, or the like; W1 and W2 each independently stands for —O—, —CH2—, or the like; Y1, Y2, Y3 and Y4 stand for —CH—, —CF—, —N—, or the like; Z stands for lower alkyl, an aliphatic heterocyclic group, or the like; Ar is a mono- or bi-cyclic aliphatic heterocycle or an aromatic heterocycle; and n is an integer of 1 to 8]. The compounds act as antagonist against melanin-concentrating hormone receptor and are useful as drugs for central diseases, circulatory diseases, or metabolic diseases.