To provide a fixing unit capable of preventing the cracking of a heating body by suppressing the rising of the temp. of the end part of the heating body as low as possible, even if small-sized sheets of paper are consecutively fixed and further, obtaining excellent fixability by preventing a temperature difference from being made in both end parts of the heating body, and a copying device provided with the fixing unit.

In the fixing unit provided with the heating body and a film which comes into contact with the heating body and is moved together with sheets of paper, to heat/fix a toner image on the paper by the heating body, with the film, the heating body consists of a main heating body H1 and a subheading body H2 and the main heating body H1 is formed such a size that sheets of paper having a maximum size in the axial direction of the heating body can be thermally fixed. Then, a central part temperature detecting means 51 is provided in the central part and an end part temperature detecting means 52 is provided in the end part. On the other hand, the subheating body H2 consists of a nondivided single body and a subheating body temperature detecting means 53 is provided in the central part. Then, the subheating body H2 is arranged on the upstream side in the carrying direction of the paper and the main heating body H1 is arranged on the downstream side.