PURPOSE: To save energy and to shorten first printing time, in an image forming device forming/carrying a thermal fixing actual image on a recording material by a printing means and processing the fixing of an image by an image heating/fixing means.

CONSTITUTION: The image heating/fixing means 9 has a heating source 93, and a heat transmitting layer member 94 being directly in contact with the heating source 9 and having heat insulatability, and adopts a constitution so that the image carrying surface of the recording material P is directly press-contacted to the surface of the side opposite to the heating source contact side of the heat transmitting layer member 94, or press-contacted to the surface of a mold-released layer formed on the above- mentioned surface, and the heat of the heating source is applied to the recording material via the heat transmitting member 94 or through this and the molt-released layer, to heat the recording material. When a device stands by for the input of a printing signal, the heating source 93 of the fixing means 9 stands by without being operated, and when the printing signal is received, the heating of the heating source 93 is started, and simultaneously, the printing action of the printing means is started, so that the printing action is executed independently of the fact that the fixing means 9 obtains a temp. capable of fixing.