A scroll compressor comprising: a rotation shaft; a fixed scroll including a fixed spiral wall; a movable scroll including a movable spiral wall engaged with the fixed spiral wall, wherein the movable scroll orbits when the rotation shaft is rotated; a compression chamber defined between the fixed spiral wall and the movable spiral wall, wherein the compression chamber has a volume that is decreased when the movable scroll orbits, and refrigerant is compressed in the compression chamber when the volume is decreased; a shaft support that supports the rotation shaft, wherein the shaft support and the fixed scroll are arranged at opposite sides of the movable scroll; a housing that accommodates the rotation shaft, the fixed scroll, the movable scroll, and the shaft support; a movable member (28, 91) arranged in the shaft support and configured to be movable in an axial direction of the rotation shaft toward and away from the movable scroll; a rotation restriction mechanism configured to restrict rotation of the movable scroll, wherein the rotation restriction mechanism includes a cylindrical pin (27b, 27B), which is arranged in one of the movable scroll and the movable member (28, 91), and a circular hole (27a, 911), which is arranged in the other of the movable scroll and the movable member (28, 91), the cylindrical pin (27b, 27B) is loosely fitted into the circular hole (27a, 911), and at least one of the cylindrical pin (27b, 27B) and the circular hole (27a, 911) includes a small diameter portion (271b, 91a) and a large diameter portion (272b, 91b); characterized in that, an orbital radius switching mechanism is configured to move the movable member (28, 91) in a first direction along an axis of the rotation shaft when a rotation speed of the rotation shaft is increased, which decreases an orbital radius of the cylindrical pin (27b, 27B) relative to the circular hole (27a, 911) so that an orbital radius of the movable scroll is decreased, and is configured to move the movable member (28, 91) in a second direction, which is opposite to the first direction, when the rotation speed of the rotation shaft is decreased, which increases the orbital radius of the cylindrical pin (27b, 27B) relative to the circular hole (27a, 911) so that the orbital radius of the movable scroll is increased. a rotation shaft; a fixed scroll including a fixed spiral wall; a movable scroll including a movable spiral wall engaged with the fixed spiral wall, wherein the movable scroll orbits when the rotation shaft is rotated; a compression chamber defined between the fixed spiral wall and the movable spiral wall, wherein the compression chamber has a volume that is decreased when the movable scroll orbits, and refrigerant is compressed in the compression chamber when the volume is decreased; a shaft support that supports the rotation shaft, wherein the shaft support and the fixed scroll are arranged at opposite sides of the movable scroll; a housing that accommodates the rotation shaft, the fixed scroll, the movable scroll, and the shaft support; a movable member (28, 91) arranged in the shaft support and configured to be movable in an axial direction of the rotation shaft toward and away from the movable scroll; a rotation restriction mechanism configured to restrict rotation of the movable scroll, wherein the rotation restriction mechanism includes a cylindrical pin (27b, 27B), which is arranged in one of the movable scroll and the movable member (28, 91), and a circular hole (27a, 911), which is arranged in the other of the movable scroll and the movable member (28, 91), the cylindrical pin (27b, 27B) is loosely fitted into the circular hole (27a, 911), and at least one of the cylindrical pin (27b, 27B) and the circular hole (27a, 911) includes a small diameter portion (271b, 91a) and a large diameter portion (272b, 91b); characterized in that, an orbital radius switching mechanism is configured to move the movable member (28, 91) in a first direction along an axis of the rotation shaft when a rotation speed of the rotation shaft is increased, which decreases an orbital radius of the cylindrical pin (27b, 27B) relative to the circular hole (27a, 911) so that an orbital radius of the movable scroll is decreased, and is configured to move the movable member (28, 91) in a second direction, which is opposite to the first direction, when the rotation speed of the rotation shaft is decreased, which increases the orbital radius of the cylindrical pin (27b, 27B) relative to the circular hole (27a, 911) so that the orbital radius of the movable scroll is increased.