Irradiation area control method for illumination light of motorcycle and illumination light for motorcycle

To provide an irradiation area control method for an illumination light of a motorcycle capable of always controlling an irradiation area of the illumination light of the motorcycle in response to read ahead operation of a rider. When the motorcycle 10 enters a corner, the first illumination lights 20a, 20b at a side corresponding to an indication direction of a turn indicator are automatically lighted interlocked with operation of the turn indicator. After the motorcycle 10 enters the corner, when it travels on the corner, the second illumination lights 21a, 21b at the same side as a side where the first illumination lights 20a, 20b are lighted are automatically lighted when a bank angle of the vehicle 10 becomes a predetermined value or higher. Aim is taken such that the irradiation areas 15a, 15b of the second illumination lights 21a, 21b in screen luminous intensity distribution at standing of the vehicle becomes upper than the irradiation areas 14a, 14b of the first illumination lights 20a, 20b.