PURPOSE: To improve noise characteristics to a great extent by forming a suction side circular muffler between the suction port of a casing and a suction side linear muffler, and also forming a discharge side muffler between the discharge port of the casing and a discharge side linear muffler on the side surfaces of the respective casings in the axial direction.

CONSTITUTION: In a vortex blower wherein the suction and discharge ports 19 and 20 of a casing 4 are located just above the casing and linear mufflers 7 and 8 are disposed just beneath a motor 6, both a suction side and a discharge side circular muffler 14a and 14b are provided, which connect the suction and the discharge port 9 and 10 to respective linear mufflers 7 and 8, and these circular mufflers are provided for the side surface of the casing 4 at the motor 6 side in such a way as to be formed into a circular passage in a rectangular shape in cross section. In addition, acoustic material 16 is bonded in the insides of the respective circular mufflers 14a and 14b. Since the length of these circular mufflers 14a and 14b is roughly 2.5 times as long as the length of the linear mufflers 7 and 8, the whole length of both of the mufflers is roughly 3.5 times as long as that of former ones, noise suppression effect can thereby be enhanced to a great extent.