A reference circuit, which is applied to a ferroelectric random access memory device, includes a polarization state detection circuit having dummy cells with ferroelectric capacitors. The detection circuit checks polarization states of the ferroelectric capacitor in the dummy cells using dumping voltages of different levels, and generates pass/fail signals as a check result. The generated pass/fail signals are decoded, using themselves as selection information for selecting one of reference voltages, of different levels, which are generated from a reference voltage generation circuit. Thus, it is possible to generate an optimal reference voltage, which senses a ferroelectric capacitor polarization state that is changed with time.