A disc brake device, comprising: a disc rotor which rotates integrally with a wheel about a rotational axis; and a caliper comprising: a piston for pressing friction pads (17, 18), which are opposed to friction surfaces of the disc rotor, toward the friction surfaces along with an increase in pressure of a brake fluid; and a cylinder for supporting the piston in a fluid tight manner so as to allow the piston to advance and retreat, the disc brake device further comprising a retraction mechanism provided to the piston, the retraction mechanism being configured to use the pressure of the brake fluid supplied to the cylinder for advancing the piston, and to retreat the piston, which has advanced for pressing the friction pads (17, 18), along with a decrease in the pressure of the brake fluid, wherein the retraction mechanism comprises: reversing means for reversing an advancing force for advancing the piston along with the increase in the pressure of the supplied brake fluid into a reversing force to be applied in a retreating direction of the piston; reversing force transferring means for transferring the reversing force generated by the reversing means in the retreating direction of the piston; and restoring force imparting means which is provided between the piston and the reversing force transferring means, and is deformed by the piston which advances due to the advancing force and the reversing force transferring means to impart a restoring force generated against the deformation to the piston, and wherein the retraction mechanism is configured to use the reversing force generated through the reversing by the reversing means, and to retreat the piston, which has advanced for pressing the friction pads (17, 18), along with the decrease in the pressure of the brake fluid, the disc brake device being characterized in that the reversing force transferring means is relatively stroked in the retreating direction of the piston to transfer the reversing force generated by the reversing means, and that the reversing force transferring means is relatively stroked in the retreating direction of the piston by an amount larger than an advancing stroke of the piston to transfer the reversing force generated by the reversing means. a disc rotor which rotates integrally with a wheel about a rotational axis; and a caliper comprising: a piston for pressing friction pads (17, 18), which are opposed to friction surfaces of the disc rotor, toward the friction surfaces along with an increase in pressure of a brake fluid; and a cylinder for supporting the piston in a fluid tight manner so as to allow the piston to advance and retreat, a piston for pressing friction pads (17, 18), which are opposed to friction surfaces of the disc rotor, toward the friction surfaces along with an increase in pressure of a brake fluid; and a cylinder for supporting the piston in a fluid tight manner so as to allow the piston to advance and retreat, the disc brake device further comprising a retraction mechanism provided to the piston, the retraction mechanism being configured to use the pressure of the brake fluid supplied to the cylinder for advancing the piston, and to retreat the piston, which has advanced for pressing the friction pads (17, 18), along with a decrease in the pressure of the brake fluid, wherein the retraction mechanism comprises: reversing means for reversing an advancing force for advancing the piston along with the increase in the pressure of the supplied brake fluid into a reversing force to be applied in a retreating direction of the piston; reversing force transferring means for transferring the reversing force generated by the reversing means in the retreating direction of the piston; and restoring force imparting means which is provided between the piston and the reversing force transferring means, and is deformed by the piston which advances due to the advancing force and the reversing force transferring means to impart a restoring force generated against the deformation to the piston, and reversing means for reversing an advancing force for advancing the piston along with the increase in the pressure of the supplied brake fluid into a reversing force to be applied in a retreating direction of the piston; reversing force transferring means for transferring the reversing force generated by the reversing means in the retreating direction of the piston; and restoring force imparting means which is provided between the piston and the reversing force transferring means, and is deformed by the piston which advances due to the advancing force and the reversing force transferring means to impart a restoring force generated against the deformation to the piston, and wherein the retraction mechanism is configured to use the reversing force generated through the reversing by the reversing means, and to retreat the piston, which has advanced for pressing the friction pads (17, 18), along with the decrease in the pressure of the brake fluid, the disc brake device being characterized in that the reversing force transferring means is relatively stroked in the retreating direction of the piston to transfer the reversing force generated by the reversing means, and that the reversing force transferring means is relatively stroked in the retreating direction of the piston by an amount larger than an advancing stroke of the piston to transfer the reversing force generated by the reversing means.