A disc-positioning mechanism of a car-mounted disc player includes drive chassis having at least a turntable and a pickup; a clamper-supporting member movable so as to come close to or detach away from the drive chassis; a clamper rotatably supported on the clamper-supporting member and being able to clamp a disc between the clamper and the turntable; and at least one positioning member abutting against the outer periphery of a disc inserted from a slot of the disc player so as to position the disc with respect to the turntable. The positioning member includes an abutment abutting against the outer periphery of the disc and a regulatory portion extending farther toward the slot than the abutment and is supported on either one component of the drive chassis and the clamper-supporting member, and the regulatory portion abuts against the other component.