This invention relates to a benzimidazole derivative of the general formula [I] ##STR00001## [wherein B.sup.1, B.sup.2, and B.sup.3 represent hydrogen atom or lower alkyl; R.sup.1 and R.sup.2 are same or different and represent lower alkyl, etc.; R.sup.3 and R.sup.4 represent hydrogen atom, etc.; W represents a 3 to 8-membered aromatic or alphatic heterocycle, etc.; and Ar represents a substituted or unsubstituted aromatic heterocycle, etc.] This compound functions as an antagonist to melanin-concentrating hormone receptor and is useful as a drug for central diseases, circulatory diseases and metabolic diseases.