Cooling device of friction stir welding machine

The invention discloses a cooling device of a friction stir welding machine. The cooling device comprises a structural shaft sleeve, a sealing frame, a baffle plate, a cover plate and a circulating oil circuit, wherein the structural shaft sleeve is fixed on a head of the friction stir welding machine; the annular sealing frame is arranged on the inner wall of the structural shaft sleeve; a stirring shaft on the head extends out of the sealing frame; an oil cooling sealing cavity is formed by the structural shaft sleeve, the sealing frame and the stirring shaft; an oil inlet and an oil outletwhich are connected with the circulating oil circuit are formed in the structural shaft sleeve; the baffle plate is arranged at an opening of the structural shaft sleeve; the cover plate is fixed onthe baffle plate through a fastener; and the aperture of a central hole of the baffle plate is larger than the diameter of the stirring shaft, so that a cavity for containing a gas cooling medium is formed in a position between