Irradiation by ultraviolet (UV)B is known to increase the number of dopamine (Dopa)-positive melanocytes in the skin. In this study, a 2.5-kJ/m2 dose of UVB radiation was delivered by a sunlamp to the ear or the eye of wild-type C57BL/6j mice and of gp91 phox−/− C57BL/6j mice that had a knockout mutation of the gp91 phox subunit of reduced nicotinamide adenine dinucleotide phosphate oxidase (NADPH). The degree of change in the Dopa-positive melanocyte expression in was reduced in gp91 phox−/− mice given UVB irradiation to the eye, but not in those given irradiation to the ear. The plasma level of α-melanocyte-stimulating hormone (α-MSH) in the blood increased in the C57BL/6j mice after irradiation to either the eye or the ear, but it did not increase in the gp91 phox−/− mice given UVB irradiation to the eye. Both gp91 phox and α-MSH in the central nervous system seem to contribute to pigmentation after UVB irradiation of the eye in mice.