A fixing unit that is provided in an image forming device and fixes a toner image transferred to paper is constructed of two belts, belt guides each of which guides the inner periphery of each of the belts, a heating member arranged in one of the belts or heating members arranged in both of the belts, a drive roller for driving the inner periphery of the belt, wherein the belts pinch paper on both surfaces thereof by the belt guides and carry the paper. This construction can realize a fixing unit reduced in size and capable of printing images at high speeds and shortening a rise time that elapses until the fixing unit reaches a fixable temperature.