PURPOSE: To control the load allocation to a plurality of motors optimally.

CONSTITUTION: A table is set so that the load allocation ratio where the total loss of motors A and B becomes the minimum value is obtained. The table is referred to from the number of revolution N and the torque command. The torque commands are allocated to the motors A and B from the obtained load allocating ratio. The total loss of the motors A and B becomes the minimum value by controlling an inverter 26 from the allocated torque commands, and the high efficiency operation is obtained. The temperature rising of the motors A and B is suppressed by setting the assignment of the torque allocation in response to the result of the comparison of temperatures tA and tB.