In a bridge circuit (10), a series circuit (11) is formed in such a manner that a resistor (R1) and a resistor (R2) are connected in series, and a resistor (R2) and a resistor (R4) are connected in series. In the bridge circuit (10), the series circuit (11) and a load section (R3) are connected in parallel, one end of a resistor (R5) is connected to a point between the resistor (R2) and the resistor (R4), and the other end of the resistor (R5) is connected to a point between the resistor (R1) and the load section (R3). In the bridge circuit (10), a voltage supply (20) is connected to a point between the resistor (R1) and the resistor (R2). A control unit (40) detects an abnormality in the load section (R3) on the basis of the detected voltage across the bridge circuit (10) detected by applying a voltage (V) from the voltage supply (20) while a switch (3) is off. This structure enables an abnormality detection device (1) to detect an abnormality while limiting the increase in size of the device.