Direct burning of ammonia is required to reduce the consumption of fossil fuels. However, ammonia has an exceedingly low laminar burning velocity. Therefore, it is necessary to improve the burning velocity of ammonia. In this study, the effect of nonequilibrium plasma on the problems of ammonia combustion is investigated. To reduce a calculation load from the difference of time scale, simulation is conducted in two stages: a section of nonequilibrium plasma discharge on a mixture and a section of combustion. The reactions of plasma discharge in a flow reactor are simulated as a perfect stirred reactor (PSR) using the SENKIN code in the CHEMKIN-II package. Second, the laminar flame located downstream of the flow reactor is simulated using the PREMIX code in the CHEMKIN-II package. From the simulation results, as the time of the application of the electric field increases, the amount of decomposed ammonia in the unburned gas increases and the laminar burning velocity becomes considerably fast. Moreover, it could be concluded that the increase of the H atom by the nonequilibrium plasma discharge has a dominant effect on increasing the laminar burning velocity of ammonia flame.