To provide a method for thermally developing a thermally developable photographic sensitive material having good flatness after thermal development and free of a print blur fault.

In the method for thermally developing a thermally developable photographic sensitive material, the thermally developable photographic sensitive material which ensures 0 mm/50 cm to 4 mm/50 cm respective curvature quantities of the end parts of four sides after thermal development and undergoes -0.05 to +0.05% dimensional change under heating at 120°C for 30 sec in both the longitudinal direction and width direction is thermally developed after heating at 1-15°C/sec.