To provide a photothermographic image forming material ensuring low fog, high sensitivity and high density and excellent in image preservability and to provide a photothermographic image forming method less liable to cause unevenness in interference in image formation and giving a uniform finish of development.

In the photothermographic image forming material having a photosensitive layer containing photosensitive silver halide grains having 20-80 nm average grain diameter, a phthalazin compound, an organic silver salt, a reducing agent and a binder on the base, the photosensitive layer has a first photosensitive layer closer to the base and a second photosensitive layer remoter from the base, the content (g/m2) of the photosensitive silver halide grains in the first photosensitive layer is lower than that in the second photosensitive layer and the content (g/m2) of the phthalazin compound in the first photosensitive layer is higher than that in the second photosensitive layer.