A method of processing a photothermographic material by a thermal processor is disclosed, wherein the photothermographic material comprises on one side of a support a light-sensitive layer containing an organic silver salt, silver halide grains, a binder and a reducing agent and a light-insensitive layer and on the other side of the support a back coating layer; the thermal processor uses a transport system in which a feed roller is disposed with being in contact with a bundle of plural stacked film sheets of the photothermographic material so as to feed the uppermost film sheet of the bundle of film sheets through rotation of the feed roller to expose and develop the fed film sheet; the light-insensitive layer or the back coating layer contains a lubricant having a mass average molecular weight of 550 or more.