To provide a drive device for motor-driven compressor which is capable of preventing a movable compression part from rotating reversely, noise and vibration from occurring without destroying the transistor of an inverter.

This drive device is provided with an inverter 15 having six transistors TrU+-TrW- for supplying phase current to a three-phase d.c. motor 12, and a control circuit 14 which generates a driving control signal for controlling the switching actions of the respective transistors TrU+-TrW- for a compressor 11 body including a compressing part 13 driven by the three-phase d.c. motor 12 formed by connecting respective exciting coils 121, 122, 123. The control circuit 14, when stopping the compressor 11 body through the three-phase d.c. motor 12 by the driving control signal, turns off all transistors Try+-TrW- for a short time, and turns on lower arms (TrU-, TrV-, TrW-) for a prescribed time with upper arm (TrU+, TrV+, TrW+) turned off.