PURPOSE: To enable the boarding of a worker while reducing the floor space on a return route and to reduce the fatigue by storing the right and left auxiliary trucks under a truck on the return route and pulling out the auxiliary truck in the case of a part assembly work.

CONSTITUTION: At the time when a work boarding truck 1 is traveled in an empty state to a work loading place, pantograph links 14, 15 are folded. Movable bearings 22, 23 pivotaly supporting movable points 14d, 15d are located at the outer ends of guide rails 20,21, and auxiliary trucks 5, 6 are stored inside storing spaces 8, 9 and fixed by a stopper 43. After loading a work on a boarding truck 1, a handle 42 is turned, a rotating shaft 41 is rotated to escape the stopper 43, the auxiliary trucks 5, 6 are pulled out and laterally moved to a use position by being escaped from the inside of the storing space 8, 9 and a universal wheel 10 is deflected transversely. When the auxiliary trucks 5, 6 are pullet out, the pantograph links 14, 15 reach the extension limit, the movable bearings 22, 23 reach the inner end side stroke ends of the guide rails 20, 21, the rotating shaft 41 is reversely rotated by the energizing force of a spring 44 to fix the movable bearings 22, 23.