A benzimidazole derivative or a salt thereof expressed by the following Formula (I): wherein one of A and B is a hydrocarbon group of C10-30 expressed by R1 and the other is -(CH2)n-NR2R3 R2 and R3 individually represent H, lower alkyl, phenyl or benzyl, or -NR2R3 may be a heterocycle having 3-7 members, or -CONR5-(CH2)n-NR2R3 may be the following Group (W): wherein R2 is H, lower alkyl, phenyl or benzyl and ring E is a heterocycle of 6 or 7 members R4 is selected from the group consisting of H, halogen, cyano, trifluoromethyl, lower alkyl and etc. R5 is H, lower alkyl, lower acyl or lower alkylcarbamoyl m is 0 or 1 and n is an integer of 0-5. The benzimidazole derivative or the salt thereof has excellent hair growth and regrowth promoting effects, which are useful for care, improvement or prevention of hair loss in mammals and, in particular, in human.
