PURPOSE: To eliminate the dynamic interference of each mutual driving parts, by composing it so that the load moving mechanism and arm telescopic mechanism provided inside of a robot arm in advance for the changing state by catching the gravity change by a force sensor from the case of transferring a heavy weight body to the case of holding nothing are properly acted.

CONSTITUTION: Loads 4a, 4b are provided on the 3rd, 4th arms 3c, 3d in a horizontal articulated arm and moving mechanism 5a, 5b for moving the loads 4a, 4b along 3rd arm 3c and 4th arm 3d individually respectively are provided. Moreover, a force sensor 9 is provided in the holding mechanism 8 for holding the object 10 provided on this 4th arm 3d. The movements of the loads 4a, 4b are controlled by a control unit 11 according to the signal transmitted from the force sensor 9 and also the dynamic interference component caused between a 1st prime mover 1 and 2nd prime mover 2 is offset.