In this paper, a numerical solution of electromagnetic pulse propagation for the case of two-dimensional rectangular area bounded by perfectly conducting walls with included perfectly conducting various-shape object has been considered. A numerical algorithm has been developed using finite difference in time-domain with NVIDIA CUDA technology implementation. A finite difference method implementation for the case of computation by graphical processor has been considered. The results of numerical modeling of a plane wave pulse scattering in the square waveguide with included cylindrical object has been shown. Comparative analysis of the performance for CPU and GPU has been carried out. It is shown, that the FDTD method computation by graphical processor provides a sufficient gain in the performance.