When a solid such as a utensil or a structure thing moves, stability is high, it is suitable for the indoor use, furthermore to provide the caster which can use the foot part of robot walking by the two pairs. A caster is comprised of a rocking shaft which sets up a wheel, a stably supporting leg, a slidably stabilizing plate and wheel, a drive device which rocks a rocking shaft and change an angle of a slidably stabilizing plate, the detection device which detects a change in the angle and the detection devices which detect a change in the increased weight. And stability is higher than the existent caster, the caster with sled for getting over obstacles which can brake without controlling the movement of the wheel of the existent caster and the axle which holds a wheel by the mechanism such as the brake for braking, in other words, a caster for the robot can be made.