To make it possible to prevent the generation of oscillation even when the variation of voltage gain is reduced due to the variation of a load, the linearity of an I/O characteristic is improved or the condition of the load is deteriorated.

This constant voltage power circuit provided with a transistor(TR) Tr1 for controlling output voltage, an error amplifier circuit OP for comparing the divided voltage of output voltage with reference voltage Vr and amplifying its error and a TR Tr2 for driving the TR Tr1 by an output from the circuit OP is also provided with a resistor R4 for connecting the collector of the TR Tr1 to the emitter of the TR Tr2 and a resistor R5 for connecting between the emitter of the TR Tr2 and ground so as to apply local negative feedback to an output stage. Since the voltage gain of the output stage is set up to an almost fixed value, frequency and I/O characteristics can be improved and a phase margin is also increased, so that the generation of oscillation can be prevented and reliability can be improved.