Castor

The utility model discloses a castor which can ensure that the relative position of an inner castor and an outer castor is fixed. The castor comprises the inner castor and the outer castor, wherein the inner castor is used for installing a rotating shaft, and the outer castor is arranged on the outer side of the inner castor. An annular boss is arranged in the middle of the annular side face of the inner castor. The two sides, on the annular side face of the inner castor, of the annular boss form a pair of circular beads. A plurality of connecting through holes are formed in the surface of the annular boss. An annular groove matched with the annular boss is formed in the middle of the annular side face of the inner side of the outer castor. Connecting columns corresponding to the connecting through holes in a one-to-one mode are arranged on one pair of side faces of the annular groove. The castor can be widely used in various universal wheels.