A crystal oscillator tester includes first and second test pins, first and second transistors, an indicator, a first diode, and first-third capacitors. The first test pin is connected to a power source. The collector of the first transistor is connected to the first test pin. The base of the second transistor is connected to the second test pin. The emitter of the first transistor is grounded via the indicator. The base of the first transistor is connected to the cathode of the first diode. The anode of the first diode is connected to the first test pin via the first and second capacitors one by one in series. The emitter of the second transistor is connected to a node between the first and second capacitors. The collector of the second transistor is grounded. The third capacitor is connected between the base and emitter of the second transistor.