Disclosed is a simulation apparatus including an input unit, storage unit, arithmetic unit, controller, and output unit. The input unit inputs a first potential at the source end, which corresponds to the gate end of a TFT, on that surface of a thin polysilicon film which faces the gate, a second potential at the source end on the back surface of the thin polysilicon film on which the gate is formed, a third potential at the drain end, which corresponds to the gate end of the TFT, on that surface of the thin polysilicon film which faces the gate, and a fourth potential at the drain end on the back surface of the thin polysilicon film. A drain current is calculated by performing an arithmetic operation on the basis of the first to fourth potentials, and a model is formed by including defect states.