Impeller and rotating machine provided with same

An impeller comprising:

• a disc that is supported by a rotating shaft and rotates about an axis of the rotating shaft;
• and
• a plurality of blades that are provided to lie substantially in a radial direction on the disc,
• wherein a flow passage is formed between the blades, and a fluid is delivered radially outward from a rotation center along each of the blades by the rotation of the disc,
• wherein, in a case where an angle formed on a backward side in a rotational direction of the disc and an outer peripheral side of the disc among angles formed between a tangent line to a projection curve line obtained by projecting a center curve line of the thickness of the blade onto the disc from the direction of the axis of the rotating shaft and an imaginary line orthogonal to a straight line connecting a tangent point between the projection curve line and the tangent line is defined as a blade angle,
• the blade angle of the blade has a predetermined increase region and a decrease region from the center towards the outside, and
• a partial decrease region having a smaller blade angle decrease amount than the blade angle increase amount of the increase region is provided at the center of an inflection region between the increase region and the decrease region,
• the blade angle of the blade is a blade angle on a hub side of the blade,
• wherein, in the blade, in a case where the flow-direction position of a leading edge that is an inlet side into which a fluid flows is 0%, and the flow-direction position of a trailing edge that is an outlet side from which the fluid flows out is 100%, the partial decrease region is formed within a range of 20% or more and 50% or less.