Abstract: [Problem] To provide a melanin concentrating hormone receptor antagonist useful as medicines for central system disorders, cardiovascular disorders, metabolic disorders. [Means for Resolution] Provided are compound of a formula (I): [wherein R1 a and R1 b each are a hydrogen atom, etc.; R2 is a hydrogen atom, a C1-6 alkyl, etc.; Ar1 is a 6-membered aromatic carbocyclic group or a 6-membered aromatic nitrogen-containing heterocyclic group; Ar2 is a group to be formed by removing two hydrogen atoms from a 6-membered aromatic carbon ring, a 6-membered aromatic nitrogen-containing hetero ring, etc.; Ar3 is a mono- or bi-cyclic aromatic carbon ring or aromatic hetero ring; m1, m2, m3 and m4 each are independently 0, 1, 2, 3 or 4, provided that the total of m1 and m2 is from 2 to 6, the total of m3 and m4 is from 2 to 6]. The compounds are useful as medicines for central system disorders, cardiovascular disorders, metabolic disorders.