A blower according to the present invention has: a spiral casing having a suction port that is open; and an impeller that is provided with a disk-shaped main plate, a ring-shaped side plate, and a plurality of blades placed between the main plate and the side plate. The impeller is housed inside the spiral casing. The blades include first blades placed on the main plate side, and second blades placed between the first blades and the side plate, wherein the second blade exit angle at the outer peripheral trailing edge of each second blade is constituted by an angle that is different from the first blade exit angle at the outer peripheral trailing edge of each first blade, and the positive-pressure surface of each second blade and/or the negative-pressure surface of each second blade has a flat part extending from the outer peripheral trailing edge to the inner peripheral leading edge.