An impeller comprises an impeller body, a plurality of stems, a blade mounting member, and a plurality of blades. The stems radially extend with one end of each stem fixed to a portion of a circumferential wall of the impeller body in the vicinity of a suction port, and are arranged at intervals in a circumferential direction of the circumferential wall. The stems assist the impeller to suck air Jn an axial direction through a suction port during rotation of the impeller. The blade mounting member is disposed concentrically with the circumferential wall of the impeller body. The other end of each stem is fixed to the blade mounting member. The blades are arranged at intervals in the circumferential direction and extend along an axial line toward a second wall portion, with one end of each blade fixed to the blade mounting member.