To provide an air conditioner with an electric compressor driven by high voltage, capable of improving the safety of occupants and mechanics, reducing the size and weight, and improving the reliability.

This driving device of an electric compressor comprises an electric compressor compressing a refrigerant for air conditioning, a DC power source as a power source of the electric compressor, a condenser connected in parallel with the DC power source, an opening and closing device mounted between the DC power source and the condenser, and opened in the stop of the electric compressor, a driving device converting the power supplied from the DC power source through the opening and closing device and the condenser into the power for driving the electric compressor and outputting the same, and a controller for instructing the operation and the stop of the electric compressor to the driving device, and the driving device is provided with a discharge control part for discharging the electric charge of the condenser by using the electric compressor after the stop of the electric compressor is instructed.