PURPOSE: To suppress noise without making air capacity small by installing a cylinder made of plural concentric thin cylinder members between an inlet port and a bucket.

CONSTITUTION: The rotary axis of a motor 2 juts out toward the side of an inlet port 1a and a bucket 5 for sending wind to discharge port side is coaxially installed thereto. The outside diameter of this bucket 5 is a little smaller than the inside diameter of a case 1 and a gap g is present between them. Between the discharge port and the bucket 5, there lies a member 4 which becomes a resistance against wind flow. The outer most thin cylinder member 6a of a cylinder 6 consisting of plural thin cylinder members 6a, 6b, 6c has a smaller outside diameter than the inside diameter of the case 1 and further the outside diameter of the bucket 5 to form a space S1. Between the thin cylinder members 6a and 6b; and 6b and 6c, a little smaller space S2 than the space S1 is formed.