A modeling circuit includes a field-effect transistor, a first current source, a first bipolar transistor, a second current source and a second bipolar transistor. The first bipolar transistor and the second bipolar transistor are parasitic bipolar transistors that are arranged symmetrically to each other. Therefore, the modeling circuit can be used in simulating the field effect transistors reflecting electrostatic-discharge characteristic regardless of the polarity of a source and a drain.