To provide an abnormal voltage detection circuit which can detect an undervoltage and an overvoltage by a simplified circuit.

When a detection voltage VS of an input terminal 11 is not higher than a lower limit voltage VL set at a Zener diode 21, a transistor 25 is turned off and a warning current flows to a resistor 32 through a resistor 24 and a diode 26. On the other hand, when the detection voltage VS is not lower than an upper limit voltage VH set at a Zener diode 31, the warning current runs to the resistor 32 through this Zener diode 31. Therefore, the warning signals to an undervoltage and an overvoltage are output to an output terminal 13.