To provide a shaft device with a bearing, on which a top body can be easily and inexpensively assembled without giving damage to the outer peripheral face of a shaft when the top body such a cam top is pressed therein.

On the outer peripheral face of the shaft 21 in the axial direction, the top body 41 and a rolling bearing 31 are arranged at a predetermined space. Between the outer peripheral face of the shaft 12 and an inner hole 42 of the top body 41 through which the shaft 12 is inserted with a slight clearance, a wedge space 50 is formed along the outer peripheral face of the shaft 12. In the state that a biting body 55 is arranged in the wedge space 50 at its wide side, the top body 41 is turned at a predetermined angle around the axis of the shaft 12 until the biting body 55 bites it in the wedge space 50 at its narrow side, whereby the top body 41 is fixed to the outer peripheral face of the shaft 12.