Disclosed are a method of promoting hair growth or preventing hair loss in a mammal. In one aspect, the method includes administering interdermally or subcutaneously an agent containing an active ingredient comprising bFGF and a pharmaceutically acceptable substance, wherein bFGF is administered in a dose of 1 μg to 100 μg per 1 cm2 of the target area of hair growth treatment or hair loss prevention and a composition for use in the method.
