A blower impeller includes a substantially cylindrical cup portion, and a plurality of blades arranged on an outer circumferential surface of a circumferential wall portion of the cup portion. The cup portion includes on an inner circumferential surface of the circumferential wall portion thereof a plurality of axially extending first ribs and a plurality of second ribs arranged between the first ribs. The first and second ribs are arranged in a circumferential direction. A virtual envelope joining radially inner end portions of the first ribs has a smaller diameter than that of a virtual envelope joining radially inner end portions of the second ribs.