A simulation apparatus of semiconductor device includes a first calculator, a second calculator, a third calculator, a fourth calculator, and a controller. The first calculator applies a voltage to an area which functions as a virtual electrode, and setting a pseudo-Fermi level of a first carrier in the area functioning as the virtual electrode to calculate a first carrier density. The second calculator analyzes continuous equation of a second carrier to calculate a second carrier density. The third calculator uses the first carrier density as a function of an electrostatic potential, and solving a first equation of the function and a Poisson's equation to calculate an electrostatic potential and the first carrier density expressed by the function. The fourth calculator calculates a current density of the first carrier to calculate a current flowing. The controller controls the voltage applied to the virtual electrode.