A constant voltage outputting apparatus includes an input terminal, an output terminal, a control unit, a plurality of output control transistors, and a switching unit. The input terminal receives an input voltage, and the output terminal outputs an output voltage. The control unit detects the output voltage and outputs a control signal equalizing the detected output voltage with a predetermined constant voltage. Each of the plurality of output control transistors receives the control signal and controls, according to the control signal, currents flowing from the input terminal to the output terminal. The switching unit switches the plurality of output control transistors to input the control signal thereto according to a predetermined setting. A constant voltage outputting method is also described.