Temperature distributions inside overdriven steady-plane shock wave fronts in Fe for shocks up to 230 GPa are evaluated by applying temperature-dependent constant-volume specific heat to the equilibrium thermodynamic theory. Equilibrium thermodynamics can be applied to these shocks and the assumption of heat transport is valid. Thus, the inside temperature distributions are evaluated fairly correctly. Overestimations of the temperature distributions inside an inviscid solid Fe mean that the viscous pressure influences greatly on the distributions. The underestimation of the constant-volume specific heat in a higher pressure region causes the overestimation of the inside temperature distributions.