The present invention includes a plurality of blades (40) that are provided at intervals in a circumferential direction on a side of a surface of a disk (30) which is rotated around an axis (O) and is directed in a direction of the axis (O). Each of the blades (40) has a primary blade (50) which extends to a rear side in a rotation direction (R) as the primary blade (50) goes from an inner side toward an outer side in a radial direction and of which a rear edge (52) is positioned on the inner side of an outer circumferential edge portion of the disk (30) in the radial direction; and a secondary blade (60) which is provided at intervals on a side in front of the primary blade (50) in the rotation direction (R), of which a front edge (61) is positioned on the outer side of a front edge (51) of the primary blade (50) in the radial direction, and of which a rear edge (62) is positioned in the outer circumferential edge portion of the disk (30).