The present invention is concerns with a spring drive used as a driving power source for a moving toy. The spring drive has a windup pinion of which at least the top of one end is formed at its rotation axis as a small diameter end having a diameter smaller than the diameter of the body thereof, and a supporting member having a supporting surface for supporting the windup pinion at the small diameter end. The windup pinion is freely rotatively supported at its small diameter end on the supporting surface of the supporting member, the friction force acting against the rotation of the pinion, is decreased.