In a non-volatile logic circuit, a first input electrode and a second input electrode are formed on a semiconductor layer and interposed between an electric current source electrode and an output electrode in a plan view. The semiconductor layer is disposed on a ferroelectric layer. A method of operating the non-volatile logic circuit includes a step of writing one state selected from four states by applying voltages to the first and second input electrode, respectively, a step of measuring current generated by applying the voltage between the electric current source electrode and the output electrode to determine, on the basis of the measured current, which of the high or low resistant state the non-volatile logic circuit has.