Fixing unit and image forming apparatus

A fixing unit for use in an image forming apparatus includes a heating roller, the heating roller being divided into a fixing area and a non-fixing area, in which the fixing area is heated to above a target temperature required for fixing of an image, and the non-fixing area has a temperature lower than the target temperature, a main coil which generates a main magnetic field for generating an induced current, and at least one secondary coil which generates a secondary magnetic field to extend an area of the main magnetic field, where the fixing area of the heating roller, when formed by the main magnetic field, has a width smaller than an entire width of a maximum size paper, and the fixing area, when formed by a combination of the main magnetic field and the secondary magnetic field, is extendable to the entire width of the maximum size paper.