A versatile vehicle speed sensor compactly disposed on the outside in a radial direction of a gear. A motorcycle includes a power unit having a torque take-out shaft for outputting a torque generated by an internal combustion engine as a drive torque for driving a rear wheel, a torque transmission mechanism T which includes a gear pair consisting of bevel gears and a drive shaft and which transmits the drive torque to the rear wheel, and a vehicle speed sensor such that teeth of a driven gear constituting the gear pair constitute a portion to be detected. The vehicle speed sensor includes a main body portion having a detecting portion opposed to the addendum of the teeth in the direction of a normal to the addendum cone surface of the driven gear, and the main body portion extends along the normal direction.