To provide low noise and high efficiency by restraining a turbulence boundary layer from being developed near the suction opening side inner surface of a shroud which forms a blower.

This blower is provided with an impeller 1 involving a plurality of blades 4 between a main plate which pivots a rotating shaft and a suction opening 5, and on the suction side of the impeller 1, a bell mouth 6 is fitted. On the suction opening 5 side of the shroud 3, a number of air passages 7 which guide stripping eddies generated at the inner surface of the part in the centrifugal direction are formed at prescribed intervals over its whole periphery, and the stripping eddies generated at the inner surface on the suction opening 5 side in the shroud 3 are guided and discharged in the centrifugal direction through the air passage 7, therefore, it is possible to restrain a turbulence boundary layer from being developed.