A multi-cylinder rotary compressor comprising: - a drive shaft including a plurality of eccentric-pin shaft portions (5c, 5d); - an electric motor configured to drive and rotate the drive shaft; - a plurality of compression mechanisms (10, 20); the plurality of compression mechanisms (10, 20) including a first compression mechanism part and a second compression mechanism part and - a sealed container housing the electric motor and the plurality of compression mechanisms (10, 20) and storing lubricating oil at a bottom thereof, each of the plurality of compression mechanisms (10,20) including - a cylinder (11, 21) having a cylinder chamber (12, 22) into which low-pressure refrigerant is sucked from a suction pressure space and from which compressed high-pressure refrigerant is discharged to a discharge pressure space, - a ring-shaped piston (13, 23) slidably attached to each of the plurality of eccentric-pin shaft portions (5c, 5d) of the drive shaft and configured to eccentrically rotate in the cylinder chamber (12, 22), - a vane (14, 24) configured to separate the cylinder chamber (12, 22) into two spaces when a front end (14a, 24a) of the vane (14, 24) is pushed against an outer peripheral surface of the piston (13, 23), - a vane groove (19, 29) housing the vane (14, 24) in such a manner that the vane (14, 24) reciprocates therein and being open to the cylinder chamber (12, 22), and - a vane rear chamber (15, 25) housing a rear end (14b, 24b) of the vane (14, 24) and communicating with the cylinder chamber (12, 22), the cylinder chamber (12, 22) always communicating with the suction pressure space, the vane rear chamber (15, 25) always communicating with the discharge pressure space, in a driven state, each of the vanes (14, 24) being applied by a first force in such a direction that the vane (14, 24) approaches the piston (13, 23) caused by a pressure difference between a pressure applied to the front end (14a, 24a) of each of the vanes (14, 24) and a pressure applied to the rear end (14b, 24b) of each of the vanes (14, 24), the second compression mechanism part having a mechanism that includes a permanent magnet disposed in the vane rear chamber and applies a second force to the vane in such a direction that the vane moves away from the piston and, thereby, applies the first force and the second force to the vane, and switches between a compressed state in which the vane is in contact with the piston and an uncompressed state in which the vane is separated from the piston and attracted by the permanent magnet and retained thereon, depending on a magnitude correlation between the first force and the second force, and a configuration in which the second force in switching from the compressed state to the uncompressed state is greater than an inertial force applied to the vane, and the pressure difference in switching from the uncompressed state to the compressed state is larger than the pressure difference in switching from the compressed state to the uncompressed state, by utilizing a property of the permanent magnet that the second force is larger in the uncompressed state in which the front end of the vane is attracted and retained on the permanent magnet than in a state in which the front end of the vane is in contact with the piston, characterized in that the second compression mechanism part includes a low-pressure introduction mechanism that introduces the low-pressure refrigerant to a space on a side of the rear end of the vane in a state in which the vane is separated from the piston. - a drive shaft including a plurality of eccentric-pin shaft portions (5c, 5d); - an electric motor configured to drive and rotate the drive shaft; - a plurality of compression mechanisms (10, 20); the plurality of compression mechanisms (10, 20) including a first compression mechanism part and a second compression mechanism part and - a sealed container housing the electric motor and the plurality of compression mechanisms (10, 20) and storing lubricating oil at a bottom thereof, each of the plurality of compression mechanisms (10,20) including - a cylinder (11, 21) having a cylinder chamber (12, 22) into which low-pressure refrigerant is sucked from a suction pressure space and from which compressed high-pressure refrigerant is discharged to a discharge pressure space, - a ring-shaped piston (13, 23) slidably attached to each of the plurality of eccentric-pin shaft portions (5c, 5d) of the drive shaft and configured to eccentrically rotate in the cylinder chamber (12, 22), - a vane (14, 24) configured to separate the cylinder chamber (12, 22) into two spaces when a front end (14a, 24a) of the vane (14, 24) is pushed against an outer peripheral surface of the piston (13, 23), - a vane groove (19, 29) housing the vane (14, 24) in such a manner that the vane (14, 24) reciprocates therein and being open to the cylinder chamber (12, 22), and - a vane rear chamber (15, 25) housing a rear end (14b, 24b) of the vane (14, 24) and communicating with the cylinder chamber (12, 22),