To improve a contact of a heating drum and of an endless belt with a heat developed photosensitive material, by making up the endless belt of a material having air permeability.

A heat developed photosensitive material A is conveyed being sandwiched between a heating drum 63 and an endless belt 65, and heated up to about 120°C by a heat source 39 provided in the heating drum 63. The endless belt 65 is made up of a material having very fine open cells. Because of this, most of gas generated at the time of processing the heat developed photosensitive material A is discharged via the very fine open cells. A surface of the heating drum 63 is roughened very finely, and therefore most of gas generated at the time of processing the heat developed photosensitive material A is discharged via very narrow gaps formed between the heat developed photosensitive material A and the heating drum 63. That is, most of the gas is discharged and prevented from being put between the heat developed photosensitive material A and the endless belt 65, and between the material A and the heating drum 63, and thereby generation of photographic density irregularity is suppressed.