PURPOSE: To eliminate the need to adjust a sensor during maintenance and to improve the detection precision and reliability of the revolving speed of a rear wheel, by providing a rotor and the sensor which detect the revolving speed of the rear wheel in a case for housing a shaft driving mechanism.

CONSTITUTION: A shaft driving type motorcycle equipped with an antiskid system has the rotor and sensor for the revolving speed of the rear wheel at a position A, B, or C in a case 38, 48, or 42 for housing the shaft driving mechanism. Consequently, it is not necessary to adjust the fitting position of the sensor during the detachment of the rear wheel, maintenance of a braking device, etc., and the detection precision and reliability of the revolving speed of the rear wheel are improved. Further, the rotor and sensor are installed in the case, so they are protected against an external obstacle and dust to prevent deterioration in performance during use.