A new numerical method has been developed to estimate the transient distributions of temperature near a friction surface in friction welding. The present method consists of the finite element method applied to a non-steady heat conduction problem and the heat input model, that is the evaluation of friction heat. To find the most proper model of heat input, empirical formulae for coefficients of friction were examined comparing with experimental data. It was found that considering the dependence of friction coefficient on temperature and friction speed gives good results.