To obtain an external preparation for the hair based on proliferation mechanism of melanocyte (chromatophore) in the hair and to provide a method for improving and preventing grey hair and both a method for improving grey hair to black hair.

This external preparation for the hair contains a grey hair improving/ preventing substance composed of melanocyte proliferation factor for promoting the proliferation of melanocyte (chromatophore) at an early phase of hair cycle. This method for improving and preventing grey hair comprises applying a melanocyte growth factor to a scalp at an early phase of hair cycle and promotes the proliferation of melanocyte so as to improve and prevent grey hair. The external preparation for the hair contains an outer root sheath melanocyte reduction controlling substance or an outer root sheath melanocyte increasing substance for controlling outer root sheath melanocyte reduction or increasing outer root sheath melanocyte. The method for improving and preventing grey hair comprises applying the substance to a scalp and controls reduction in melanocyte existing on an outer root sheath or increases melanocyte existing on an outer root sheath so as to improve and prevent grey hair.