A joint structure for an independent system designed to improve the maintenance performance of a rear wheel suspension. Rear wheel axles extend leftward and rearward from a final case supported by the rear portion of a body frame to independently suspend respective left and right rear wheels. The respective rear wheel axles are coupled to left-hand and right-hand joints on the left and right sides, respectively, of the final case. A driven sprocket engaging with a chain is attached to the left-hand joint and a separate holder is detachably attached to the front of the final case. A joint-part shaft of the right-hand joint is supported by the final case via a bearing and also a brake disk is attached thereto. A male-shaped joint-part shaft integrally extending from the left-hand joint is fitted into the female-shaped joint-part shaft for integrally rotatable coupling.