Abstract: A wheel of the present disclosure includes a barrel holder, barrel support shafts, barrels, and bearings. The barrel holder is rotationally driven. The barrel support shafts arranged on the circumference of the barrel holder at an angle to a rotation axis of the barrel holder. The barrels are barrel-shaped rotating bodies. The barrels are rotatably supported on the corresponding barrel support shafts, and outer surfaces of the barrels contact a surface on which the wheel travels as the barrel holder rotates. The bearing supports the retainer. A groove is formed at least in a region of the outer circumferential surface of the barrel support shaft extending in the axial direction and including a radially inner projected area of the retainer.