The prediction model includes the steps of calculating a surface area S1 of a control mold, measuring the force F1 for demolding from the control mold, determining first and second test specimens with respective surface areas S0, S′0, measuring the force F0 for demolding from the first test specimen, measuring the force F′0 for demolding from the second test specimen, calculating the ratio of S0 and S′0 so as to define a test specimen surface area ratio Rse, calculating the ratio of the force F0 for demolding from the first test specimen and F′0 for demolding from the second test specimen so as to define a force ratio Rfe, measuring the molding surface area Sm of a mold to be measured and calculating the force Fm for demolding from the mold to be measured such that Fm=F1×Sm/S1×Rfe/Rse.