An apparatus for protecting an inverter against over current is constructed of a plurality of switching devices connected between the positive and negative terminals of a DC power source. The apparatus has a plurality of detecting devices that convert the currents passing through the plurality of switching devices into voltages and generate detection outputs, a plurality of amplifier circuits, a plurality of comparing devices that supply the detection outputs of the detecting devices to the amplifier circuits and generate an abnormality output if an absolute value of a detection output exceeds a predetermined value, and a protecting device that interrupts the drive of all switching devices if any of the comparing devices issues an abnormality output.