PURPOSE: To prevent an axle from rotating when a nut is fastened at the end of the axle so as to improve the assembling property of a rear wheel axle device by providing two-sided notches at the head portion of the axle, forming a rib or groove at the head portion along the diameter of the axle, rotating the rib or groove by means of a tool, and pressing one of the two-sided notches against the upright wall of a washer extended along the outside of axle metal fittings, thereby stopping rotation of the axle.

CONSTITUTION: An axle 7 is passed between the right and left axle metal fittings 2 of a rear fork 1 and fastened and a rear wheel is freely rottably supported to the axle 7 and one of two-sided notches 8 provided at the head portion 9f the axle 7 is pressed against the upright wall 12 of a washer 4 extended along the outside of the axle metal fittings 2 so as to stop rotation of the axle and a rib 10 or groove 11 is formed at the head portion 9 of the axle 7 along the diametral direction of the axle and a tool is fitted into the rib 10 or groove and turned so that the two-sided notches 8 abut to the upright wall 12.