A blower providing a blower mode and a vacuum mode. A casing provides a motor housing installing a motor and a fan housing installing a centrifugal fan rotationally driven by the motor. A partition is disposed and having a first surface defining a motor housing and second surface defining a fan housing. The fan includes a generally circular base plate having one surface in direct confrontation with the second surface. A plurality of base plate through-holes arrayed in an imaginary circle whose center is coincident with the rotation axis of the fan are formed in the base plate. The partition is formed with a plurality of partition through-holes arrayed in the imaginary circle and in selective alignment with the base plate through-holes in accordance with the rotation of the centrifugal fan. Each partition through-hole includes a width increasing region where a width of the partition through-hole in the circumferential direction is gradually increased toward the second surface.