A cooling device includes a cooling roller having a dual tube structure including an inner tube disposed inside an outer tube, an outside flow passage and an inside flow passage in which a cooling medium flows, and an opening that allows the outside flow passage to communicate with the inside flow passage, a cooling medium transport unit, and a rotating tube joint unit mounted to one end side of the cooling roller. One end of the outer tube is coaxially rotatably fitted to a first fitting section of the rotating tube joint unit. One end of the inner tube is coaxially fitted into and rotatably or fixedly supported to a second fitting section of the rotating tube joint unit, and the other end is coaxially fitted into and rotatably or fixedly supported to a fitting section on the other end of the outer tube.