To provide an inverter for an automobile capable of detecting ground fault with a simple circuit constitution.

The inverter device 8 with an inverter (inverter module 35) for driving a motor by generating a pseudo AC output from a battery 1 mounted on a vehicle body B is equipped with a ground fault detection circuit 75 connected between the minus line 6 of the battery 1 and the vehicle body B, and with a controller 60. The ground fault detection circuit 75 comprises circuits in series of a resistor element 77 and capacitance element 78, or circuits in series of a plurality of resistor elements, wherein the controller 60 inputs potentials at connecting points of respective elements to detect a ground fault.