to provide a cross - flow fan that is ideal for use in an excimer laser device or fluoride laser device that is capable of high - speed rotation , that has high mechanical strength even at high - speed rotation and that does not suffer deformation , a rotating shaft is mounted passing through the center of cross - flow fan for a discharge excitation gas laser device . use of the rotating shaft facilitates alignment of the rotating shaft and high - speed rotation is possible because the mechanical strength is raised . furthermore , magnetic bearings can be used since misalignment does not develop . the flow velocity is not adversely affected even if a rotating shaft , as noted above , is utilized since a cross - flow fan for gas circulation in an excimer laser device is used under high - head , low - flow velocity conditions . deformation due to shaft weight can be reduced since the weight of the rotating shaft can be lowered by providing a hollow section within the rotating shaft , and that increases the inherent oscillation frequency which permits still higher speeds .