A speed change device for a motorcycle has a lost motion mechanism associated with a shift rod of a link mechanism that transmits an operating force applied to a shift operating member to a shift spindle. The speed change device is provided with a shift stroke sensor that detects an amount of expansion/contraction stroke of the shift rod and with a shift spindle sensor that detects rotation of the shift spindle. Further provided is an output control device that controls the output of an internal combustion engine on the basis of detection signals of the shift stroke sensor and the shift spindle sensor. The shift spindle has a detection-target recessed portion formed by recessing a part of a cylindrical outer circumferential surface of the shift spindle. The shift spindle sensor detects the rotation of the shift spindle in cooperation with the detection-target recessed portion.