To provide an image forming method which prevents heat shrinkage of a recording material during heat development so as to obtain a good image and which prevents irregular density during heat development.

The heat development including the following processes is carried out for a heat developable recording material having a heat-treated polymer film supporting body and containing a high contrasting agent. The processes are a first heating process (preheating process) to heat the recording material at <100°C under conditions which do not substantially cause the formation of an image, and a succeeding second heating process to heat the material at ≥100°C to form an image.