A pin-ring mechanism that transmits driving force to cause a driving-side scroll member and a driven-side scroll member to perform rotational movement in a same direction at a same angular velocity is provided. A driving-side end plate includes a ring member installation hole into which a ring member is inserted and installed. The ring member installation hole includes a non-wall-side hole part and a wall-side hole part. The non-wall-side hole part is formed from a non-wall-side surface and has a diameter corresponding to an outer diameter of the ring member. The wall-side hole part is formed from a wall-side surface and has a diameter smaller than the outer diameter of the ring member.