A plurality of curved rectangular blades are arranged in a circumferential direction on a periphery of a disc, forming a pipe-like basket shape with an opening on a front side of the disc. Rotation of the disc draws in air from the opening and draws out the air in a centrifugal direction through a space between the blades. The blades are formed of a thick plate part close to the disc and a thin plate part that is thinner than the thick plate part and farther than the thick plate part from the disc. A bulge serving as a boundary between the thick plate part and the thin plate part is formed on a negative pressure surface of the blades, which is of curved convex shape.