An opposed-piston type disc brake device comprising: a caliper including an outer body and an inner body which are disposed on two sides of a rotor in an axial direction of the rotor and in which cylinders (18a, 18b, 19a, 19b) are respectively provided, and a pair of coupling portions (15a, 15b) which connect two circumferential side portions of the outer body and the inner body, and configured to be fixed to a suspension device; a plurality of pistons (10, 11) respectively fitted in the cylinders (18a, 18b, 19a, 19b); a pair of pads (9a, 9b), disposed on two sides of the rotor in the axial direction, and supported so as to be displaced relative to the caliper in the axial direction; and a parking mechanism portion including a clamp member and a thrust generating mechanism, wherein the clamp member includes a pressing portion on an axial outer side portion and a clamp base portion on an axial inner side portion, the clamp member is disposed between the pair of coupling portions (15a, 15b) in a circumferential direction, crosses the pair of pads (9a, 9b) and the inner body provided between the pressing portion and the clamp base portion from radially outside, and is supported to the caliper so as to be displaced relative to the caliper in the axial direction, the thrust generating mechanism includes an inner displacement member which is supported on the clamp base portion and is configured to be displaced axially inwardly relative to the caliper during braking operation, and an outer displacement member which is disposed in one of the cylinders provided in the inner body and is configured to be displaced axially outward relative to the caliper during braking operation, the cylinders (10 11) are configured to receive a pressure oil so that a braking force by a service brake is generated, and the thrust generating mechanism is configured to be operated so that a braking force by a parking brake is generated, and a guide cylinder extending axially inward from an opening edge portion of the cylinder in which the outer displacement member is disposed is provided in the inner body at an axial inner side portion of the inner body, the clamp base portion includes a housing hole opened to an axial outer side of the clamp base portion in which the inner side displacement member is disposed, and the guide cylinder is fitted into the housing hole so as to relatively move in the axial direction, to form a first guide portion which supports the clamp member so that the clamp member is displaced relative to the cylinder in the axial direction, the opposed-piston type disc brake is characterized in that the clamp base portion includes a through hole communicated to the housing hole from an outer peripheral surface of the clamp base portion, and an opening of the through hole opened to the outer peripheral surface of the clamp base portion is closed by a stopper. a caliper including an outer body and an inner body which are disposed on two sides of a rotor in an axial direction of the rotor and in which cylinders (18a, 18b, 19a, 19b) are respectively provided, and a pair of coupling portions (15a, 15b) which connect two circumferential side portions of the outer body and the inner body, and configured to be fixed to a suspension device; a plurality of pistons (10, 11) respectively fitted in the cylinders (18a, 18b, 19a, 19b); a pair of pads (9a, 9b), disposed on two sides of the rotor in the axial direction, and supported so as to be displaced relative to the caliper in the axial direction; and a parking mechanism portion including a clamp member and a thrust generating mechanism, wherein the clamp member includes a pressing portion on an axial outer side portion and a clamp base portion on an axial inner side portion, the clamp member is disposed between the pair of coupling portions (15a, 15b) in a circumferential direction, crosses the pair of pads (9a, 9b) and the inner body provided between the pressing portion and the clamp base portion from radially outside, and is supported to the caliper so as to be displaced relative to the caliper in the axial direction, the thrust generating mechanism includes an inner displacement member which is supported on the clamp base portion and is configured to be displaced axially inwardly relative to the caliper during braking operation, and an outer displacement member which is disposed in one of the cylinders provided in the inner body and is configured to be displaced axially outward relative to the caliper during braking operation, the cylinders (10 11) are configured to receive a pressure oil so that a braking force by a service brake is generated, and the thrust generating mechanism is configured to be operated so that a braking force by a parking brake is generated, and a guide cylinder extending axially inward from an opening edge portion of the cylinder in which the outer displacement member is disposed is provided in the inner body at an axial inner side portion of the inner body, the clamp base portion includes a housing hole opened to an axial outer side of the clamp base portion in which the inner side displacement member is disposed, and the guide cylinder is fitted into the housing hole so as to relatively move in the axial direction, to form a first guide portion which supports the clamp member so that the clamp member is displaced relative to the cylinder in the axial direction, the clamp base portion includes a through hole communicated to the housing hole from an outer peripheral surface of the clamp base portion, and an opening of the through hole opened to the outer peripheral surface of the clamp base portion is closed by a stopper.