To improve workability when an operator switches and adjusts the tilting attitude of a mast stepwise in a track with an elevating deck having a mast erected for elevetably supporting the deck at the front part of a travelling machine body, the mast supported tiltably backward.

A hand-operating switch H connected to an attitude switching mechanism C for stepwise switching the mast 10 of the truck, equipped with an elevating load-platform, from a rising attitude to tilting attitudes is attached to an operating handle 16 of the truck. By interlockingly operating the hand- operating switch H with the raising operation of the operating handle 16, the tilting attitude of the mast 10 is switched stepwise.