The scroll-type compressor comprises a fixed scroll and an orbiting scroll engaged with each other; a back pressure control valve 50 inserted from the large-diameter side of the stepped-shaped pressure release passage L4 which communicates between a suction chamber H1 and a back pressure chamber H3 which applies a back pressure for pressing the orbiting scroll against the fixed scroll. The scroll-type compressor further comprises an O-ring 60 fitted in a circumferential groove 53a formed in the outer peripheral surface of the valve 50, and a ring member 61 press-fitted into the large-diameter side of the pressure release passage L4, and holds the valve 50 between the ring member 61 and the stepped portion. Then, the compressive stress is unlikely to be applied to the valve 50, and the deformation of the valve 50 is reduced to prevent the reduction in the control accuracy of the back pressure.