This study concerns numerical modelling and computer simulation of thermal phenomena in spiral laser heating of shaft made of S355 steel. 3D numerical analysis is developed for the prediction of heat affected zone in Abaqus/FEA software. Power distribution of spirally moving heat source is implemented into additional DFLUX subroutine, written in Fortran programming language. Changing with temperature thermophysical properties are assumed in the analysis. The model of heat source motion takes into account the size of heat affected zone. Results of numerical analysis include temperature field, predicted heat affected zone and cooling rates. These results are a start point for the analysis of thermomechanical phenomena with the consideration of phase transformations in solid state.