To smoothen delivery of a carried object by carrying air from a chamber between blades, forming a carrying air inlet and/or a carrying air outlet in a shape where circumferential width increases toward the radially outer side.

In an isopodous trapezoid outline of a carrying air inlet 52 and a carrying air outlet 53, diagonal lines are placed on diameters of a side plate 15, the long side of the parallel facing sides is placed on the radially outer side, the short side is a line orthogonal to a diameter of the side plate 15, and the long side is a circular arc matching to the inner periphery of a cylindrical casing. Because the carrying air inlet 52 and the carrying air outlet 53 have the isopodous trapezoid outline which expands in the radially outer direction, each part of a sector space overlaps the carrying air inlet 52 and the carrying air outlet 53 and pressing out time caused by the carrying air is uniformed. This reduces the trouble that insufficient flow of the carrying air or insufficient introduction from the sector space causes artificial snow at a specific part in the sector space to remain in the sector space.