Impeller and method of manufacturing the same

An impeller comprising:

• a hub surface formed around a rotary shaft;
• and
• a plurality of blades protruding from the hub surface, the plurality of blades being spaced apart from each other in a rotation direction of the rotary shaft, wherein
• each of the plurality of blades has a pressure surface located on a leading side of the rotation direction and a suction surface located on a trailing side of the rotation direction,
• each of the plurality of blades is provided with a plurality of first concave surfaces, each of which is formed by cutting a trace, at a boundary between the pressure surface and the hub surface,
• each of the plurality of blades is provided with one second concave surface, which is formed by a cutting trace, at a boundary between the suction surface and the hub surface,
• at least two different first concave surfaces having different concave radii in cross section are included in the plurality of first concave surfaces, and
• the different concave radii of the plurality of first concave surfaces include a first concave radius that is the largest among the different concave radii, and the first concave radius is identical to a second concave radius that is a concave radius of the second concave surface in cross section.