A caster has a ring-shaped main body, two ring-shaped wheels provided on both side end parts of the main body and two ring-shaped holders by which the two ring-shaped wheels are rotatably fitted on the main body. Each of the wheels has a first sliding face on an inner side of an inner circumferential part and a second sliding face on an outer side thereof. A first dry bearing is provided between an outer circumferential face of a ring-shaped flange provided on each of the both side end parts of the main body and the first sliding face, a second dry bearing is provided between an outer circumferential face of a ring-shaped flange provided on an outer end part of each of the holders and the second sliding face. The caster provides a high mechanical stability, durability, impact resistance and heat resistance.