A source and sink voltage regulator includes an output circuit, an amplifier circuit and a bias current control circuit. The output circuit is used to output a loading current under a stable output voltage and is further used to draw a reverse loading current while a loading voltage is greater than the output voltage. The amplifier circuit maintains the output voltage at a predetermined normal output voltage. The bias current control circuit keeps the transistors of the output circuit under a predetermined static bias current to accelerate the response speed of the voltage regulator, automatically maintaining a balance status while the output circuit is working.