A current mirror circuit includes transistors having bases coupled together and emitters connected to a voltage line. The current mirror circuit further includes a zener diode having an anode connected to the bases and a cathode connected to the voltage line. When a base potential of the transistors decreases, a reverse current of the zener diode increases. Therefore, the zener diode has a resistance and acts as a resistor to clamp the base potential of the transistors. A layout area of the zener diode is much smaller than that of the resistor having a resistance equal to that of the zener diode. The current mirror circuit achieves reduced chip size by using the zener diode instead of the resistor.