PURPOSE: To eliminae false operation such as erroneous reverse travelling by detecting the position of a slewable body to a travelling body and making thereby the diretios of operation of the travelling lever and of advance of a vehicle accord with each other in the captioned device for a loading shovel and the like.

CONSTITUTION: The travelling operation levers 11 and 12 deliver their operation with traveling signals VL and VR, while a slewing operation lever delivers a slewing angle signal Vθ in accordance with a slewing angle by means of a slewing angle detector 23 fitted to a center swivel. And, the slewing angle θ is set to be 0° when a working machine 4 is positioned properly in the front direction to the travelling body 2, while it is set 90° and 180° when the machine is positioned in the right-side and rear directions. In the case when the working machine 4 is positioned on the front side to the travelling body 2, i.e. when the angle θ is in the range from 270° to 0° and to 90°, a control signal Sb is employed as it is, and when the working machine 4 is positioned on the rear side to the travelling body 2, i.e. when the angle θ is in the range from 270° to 180° and to 90°, the control signal Sb is delivered through the intermediary of a polarity inverting circuit 32.