A transmission for a motorcycle has an input shaft, an output shaft, a plurality of speed change input gears, and a plurality of speed change output gears, and performs shifting by a shift mechanism. The speed change input gears are fixed to one of the input shaft and the output shaft, e.g., the input shaft, in the axial direction and about the axis, the speed change output gears are fixed to the output shaft in the axial direction and are fitted to be rotatable about the axis, and a plurality of slider rings for dog-coupling are fixed to the other shaft about the axis and are provided to be slidable in the axial direction. An engaging hole is formed in the slider rings, and the speed change gears on the other shaft are formed with an engaging projection which can engage with the engaging hole by the movement of the slider rings in the axial direction.