A step portion is formed at an outer peripheral surface of an axially-central portion of an outer ring, and is smaller in diameter than outer peripheral surfaces of axial opposite end portions of the outer ring. The step portion is continuously formed over an entire periphery of the outer ring, and has a predetermined width over the entire periphery. The outer peripheral surface and inner peripheral surface of the outer ring are pressed radially inwardly, and therefore are bulged radially inwardly into a step-like shape to form the step portion having an axis coinciding with a axis of the outer ring. A pedestal of a cylinder block and a cap member retain the outer peripheral surface of the step portion, thereby positioning the outer ring in the axial direction and also preventing a movement of the outer ring in the axial direction.