PURPOSE: To eliminate the unstable performance in the working condition, and reduce the aerodynamic noise by setting the sectional size on the negative pressure surface side of the leading edge part of a stator blade to be larger than the thickness of the stator blade.

CONSTITUTION: A plurality of stator blades 1 are provided in the circumferential direction at equal interval between the inner wall of a casing 2 and an inner cylinder 6 on the downstream side of an impeller 8. A leading edge part 3 has the thickness 9 of the approximately arc-shaped section which is larger than the thickness of the stator blade 1. When the fluid flows in the stator blades, this constitution provides the flow along the thickness 9 irrespective of the in-flow direction, the separation at the leading edge 3 is prevented, reduction of the air-blowing efficiency caused by the separation is prevented, and the generation of the noise can be reduced. The deflection angle of the stator blades can be changed less by the thick part even when the inlet angle and the direction of the leading edge of the stator blades are different due to the change of the direction of the suction flow according to the working condition.