The invention discloses a double-shaft-shoulder stir friction head water-cooling cooling device and a stir friction welding device and method. The double-shaft-shoulder stir friction head water-cooling cooling device comprises a cooling block and a cooling fin. One end of the cooling block is fixedly connected with a stirring needle, and the other end of the cooling block can stretch in cooling liquid. A draining groove is formed in the cooling block. The cooling fin is fixed to the upper end of the cooling block. When the cooling block rotates, the cooling liquid ascends along the draining groove and flows through the cooling fin, and therefore the temperature of a double-shaft-shoulder stir friction head is reduced. The cooling effect is good, the welding quality can be improved, the overall structure of the stir head does not need to be damaged, a cooling structure is simple, assembling is convenient, and repeated use can be achieved. In the welding process, the cooling liquid can be recycled, components of the cooling liquid can be changed according to welding requirements, and therefore the welding quality can be further improved.