This work is dedicated to research on the Selective Laser Sintering (SLS) process. The problem has been intensively investigated by many research groups. A number of physical phenomena observed in SLS are studied. There is, however, no comprehensive understanding of the true process nature and no solid theory of the SLS process has been established up to date. In this thesis, a theoretical model of the process has been developed. This model considers the laser-matter interaction, the non-linear heat diffusion and the phase transformations. The evolution of the material properties due to the sintering phenomena is analyzed by a microscopic sub-model. For solving the governing equations a numerical method based on finite element analysis has been proposed. A combination of non-conformal adaptive mesh for space discretization with a Chernoff's scheme for time discretization has been used. The results of the numerical simulations have been compared to the experimental results. The temperature field evolution predicted by the model is validated by experimental measurements performed with an infra-red camera.