In a band gap reference voltage circuit, a band gap cell circuit composed of two transistors is driven with different current densities under a bias condition in which first and second reference voltages output in accordance with the operating states of the two transistors are equal to each other, thereby outputting a band gap reference voltage from a reference voltage output line. A differential amplifying circuit that is supplied with the first and second reference voltages as differential input signals subjects the differential input signals thus supplied to differential amplification. A level shift circuit is connected between a power supply line and the reference voltage output line and supplied with an output voltage of the differential amplifying circuit to carry out a level shift operation on the output voltage concerned.