A hub is supported rotatably about an axis of rotation, and the diameter thereof increases from upstream to downstream sides along a fluid flow. A plurality of impeller blades extend radially outward from an outer circumferential surface of the hub. A shroud is formed in a cylindrical shape whose diameter increases from the upstream to downstream sides along the fluid flow and joins outer circumferential ends of the plurality of impeller blades. The impeller blades are composed of upstream blade segments and downstream blade segments bonded at a bonding surface extending in a direction substantially perpendicular to the axis of rotation. The upstream blade segments are integral with at least a portion of the shroud, and the downstream blade segments are integral with at least a portion of the hub. This improves the reliability and performance of an impeller and a compressor.