An impeller includes an impeller body which rotates about a rotation axis, and a vane which is provided at the impeller body. The impeller body receives force asymmetric with respect to the rotation axis in driving and rotation in a fluid in a manner that radially inward fluid force, which is generated due to arrangement of the vane, acts on a predetermined point in a peripheral direction. In the impeller body, a filled space filled, in a fluid, with the fluid is formed.