Positive pressure and negative pressure are alternately applied to artificial hearts so as to drive the same. Each of driving systems includes a pressure sensor, and a solenoid valve connected between a pressure source and an accumulator is controlled in its opening and closing in order that the detected pressure is made coincident with a set value. A pair of solenoid valves connected respectively to an output port of the accumulator in a positive pressure system and an output port of the accumulator in a negative pressure system are opened and closed, thereby to supply positive pressure air and negative pressure air to the artificial hearts alternately. There is also included a backup driving system, and upon receiving instruction for system switching, lamps are energized in due sequence so as to inform the operator of valves to be operated manually. Control of the solenoid valve is carried out by microcomputers, and a control board used for imparting instructions to the microcomputers includes a remote control unit which is connected to the apparatus body through a cable. The solenoid valves are installed within the corresponding accumulators.