in a motorcycle of the type including a transmission case provided on one side of a body frame , and a transmission and a gear type deceleration unit housed in the case for transmitting a driving force from an engine to an axle of the rear wheel an antilock controlling device for controlling a braking hydraulic pressure for the rear wheel includes a wheel deceleration sensor operatively connected with the rear wheel , and a casing for accommodating the antilock controlling device is attached to the transmission case . the wheel deceleration sensor includes a driving shaft having a pinion coupled thereto , and the pinion meshes with a final gear of the gear type deceleration unit . with this construction , there is no need of providing any exclusive overdrive device for the sensor , and a complication in the structure surrounding the rear wheel is avoided .