A numerical approach is proposed to estimate temperature field in toner fusing process for improvement of fusers in electrophotographic printers. The outline of the numerical calculation is as follows: 1) Finite difference method is applied to discretize the equation of thermal conduction on the computed region consisting of a heat roller, air gap, toner, paper and a pressure roller. 2) The governing equation is solved by time marching with the alternating direction implicit method. 3) The rotation of the heat and the pressure rollers and the transfer of the paper are modeled by transfer of thermal properties, the procedure in which temperature and heat stored in a cell are transferred from the cell to the adjacent outgoing cell synchronizing with the rollers' rotation. 4) Toner fusing characteristics are modeled by using a constant melting point and a latent heat. The availability of the calculation is discussed compared with the temperature obtained in measurement, indicating the necessity of the introduction of an additional resistance in thermal conduction. The temperature distribution in the fusing region is also analyzed for obtaining fundamental feature of heat transfer.