Abstract: A magnetic coupling mechanism which can transmit rotational force of a motor with high efficiency and is simple in mechanism and unlikely to damage bearings, etc. and also unlikely to contaminate a laser gas, and in which flakes from plating or the like will not cause an operational abnormality. The magnetic coupling mechanism transmits rotational force from a motor shaft outside a laser chamber filled with a laser gas to a shaft of a gas-circulating fan in the laser chamber to rotate the fan. A first magnet group is provided on an inner peripheral surface at one end of the motor shaft. A second magnet group is radially coupled to the first magnet group through a ceramic partition constituting a part of the wall of a container of the laser chamber. The second magnet group is provided on the outer peripheral surface of the fan shaft.