Provided is an impeller having a boss (2) which rotates around an axial center and a plurality of wings (3) which are provided on an outer circumferential portion of the boss (2), and a front rim (31) of the wing (3) has a smooth wave form continuously having an uneven portion in a radial direction. A pitch distance L between tips (311) of projected portions of the wave form which are adjacent to each other is increased toward the outer circumference side or is determined so as to be correlated with a distribution in the radial direction of a scale of an upstream turbulent eddy. With this structure, the upstream turbulent eddy which generates when airflow enters the wings is separated so that a length in the radial direction becomes shorter, the upstream turbulent eddy is made to be random, the development of the eddy is suppressed, and sharp discontinuity of the flow is prevented even when the eddy is separated, with the result that a noise can be reduced.