The evaluation of the temperature distribution in the tool surface layer has been strongly required to enable the accurate prediction of the tool life in tool design. The variation in the maximum temperature of a forging tool during hot forging was examined with respect to friction shear factor m, chamfer angle θ, corner radius R and contact time tc, by finiteelement analysis. Friction shear factor m greatly influenced the variation in the maximum temperature. In particular, the temperature rise at 80% reduction in area was considerable at m = 0.0-0.2. When the reduction in area exceeded approximately 80%, it was necessary to control the shear friction factor to less than 0.3. When the radius of the corner became more than 2 mm, the rise in the maximum temperature was effectively prevented. This effect was more marked when θ= 0o than when θ = 30o. The maximum temperature of forging tools can be controlled by selecting the friction shear factor (lubrication or surface modification), the chamfer angle and the corner radius appropriately. A guideline for selecting appropriate conditions in forging process design was presented on the basis of the obtained results.