A crossflow fan includes a rotary impeller formed by curved blades 42. Each of the blades 42 has an outer peripheral edge 43 close to the centrifugal side of the impeller and an inner peripheral edge 44 close to the rotation axis side of the impeller. A plurality of cutouts 45 are formed in the outer peripheral edge 43 and spaced apart at predetermined intervals. Dimples 48 for changing a boundary layer from a laminar flow to a turbulent flow are formed in a negative pressure surface 4q of each blade 42 in the vicinity of the outer peripheral edge 43 to prevent the gas flowing around the blade 42 from separating from the blade 42.