To provide a voltage abnormality detecting device in which an AC power of an overvoltage is not inputted to a power board even if the AC power of an overvoltage is inputted to a power input part, and which can surely prevent the breakage of the power board.

When an AC power of 100 V is inputted from the power input part 1 while a connector is connected to a 100V tap, a relay control part of a control part 6 brings a relay circuit 4 into an on-state by energizing an electromagnetic coil of the relay circuit 4, and when an AC power of 200V is inputted from the power input part 1 while the connector is connected to the 100V tap, the relay control part of the control part 6 keeps the relay circuit 4 in an off-state without energizing the electromagnetic coil of the relay circuit 4.