A differential amplifier circuit includes a differential input stage comprising first and second transistors whose sources are connected with each other, a constant current source connected between the sources of the first and second transistors and a ground, a current mirror circuit comprising third and fourth transistors whose sources are connected with a power supply source, a fifth transistor of a same conductive type as that of the first transistor, connected at a drain to a drain of the third transistor, connected at a source to a drain of the first transistor and connected at a gate to a reference voltage source; and a sixth transistor of a same conductive type as that of the second transistor, connected at a drain to a drain of the fourth transistor, connected at a source to a drain of the second transistor, and connected at a gate to the reference voltage source.