PURPOSE: To improve operability of a machine by installing an articulated operating arm to the operating section of a power shovel, and by making control therewith so that working members such as a bucket and an arm make swing motions in accordance with the movement of the operating arm.

CONSTITUTION: An operating arm 3, composed of a first to third swing rods that are connected one another so that they become capable of making swing motion, is installed to an operating section of a power shovel or the like. Then a hydraulic control circuit is prepared so that is enables the first, the second and the third swing rods to move corresponding respectively to a boom, an arm and a bucket of the power shovel. Then the bucket, the arm and the boom can be operated only by operation of a handle 36 and, at the same time, visual judgement on operation becomes possible. Thereby operability of the machine can be improved.