A CMOS reference voltage circuit, preferably formed on a semiconductor integrated circuit, and outputting a reference voltage having a temperature-independent characteristic, comprises first and second diode-connected transistors (or diodes), respectively grounded and driven with two constant currents bearing a constant current ratio to each other, and a unit for amplifying a differential voltage of output voltages from the first and second transistors by a preset factor and for summing the amplified differential voltage to an output voltage of the first or second transistor.