A control method for a transmission for a motorcycle having a plurality of shift gear trains such that the combination of gears meshing with each other is changed by driving an actuator to change a shift position. When a vehicle body inclination angle .beta. as a sideward inclination angle of a vehicle body of the motorcycle during running of the motorcycle becomes greater than or equal to a predetermined angle, a change in shift position in the transmission is inhibited. The method controls the transmission for the motorcycle in order to reduce an operational load on a rider during turning of the motorcycle.