An impeller includes: a boss portion driven to rotate by a motor; and a plurality of rotating blades projecting radially from the boss portion in a direction in which a diameter increases from a rotational axis of the motor and generating airflow in an axial direction of the rotational axis. The rotating blades have an S-shaped radial cross section in which an inner peripheral side portion is protruded with respect to the airflow and an outer peripheral side portion is recessed with respect to the airflow, and a recess-shaped portion of the rotating blades has a distribution of a radius of curvature value such that the radius of curvature value gradually decreases toward a blade trailing edge portion from a blade leading edge portion and a rate of the gradual reduction becomes smaller toward the blade trailing edge portion.