A cross flow fan includes a support plate and an impeller with a plurality of blades disposed on the support plate at predetermined intervals. On each blade, a radius of a pressure surface arc is greater than a radius of a suction surface arc, a radius of an inner peripheral side arc is greater than a radius of an outer peripheral side arc, and a region of maximum thickness is located 40% to 60% from the inner peripheral side arc in the lengthwise direction. The blades are disposed such that the inner peripheral side arcs are positioned on an inner peripheral side of the support plate and the outer peripheral side arcs are positioned on an outer peripheral side of the support plate. A flow path width between the plurality of blades gradually decreases from the inner peripheral side toward the outer peripheral side of the support plate.