PURPOSE: To make it possible to load, unload and discharge to and from the load-carrying platform of a vehicle by means of a single cylinder, and as well to enhance the strength thereof, by providing a slider which may move outward through an opening formed in a tiltable frame, to a vertical arm.

CONSTITUTION: A derricking frame 21 which is attached with a vertical arm 12 through a base frame 13, is mounted to a tiltable frame 27 through a shaft 39. The base frame 13 is movable through a link mechanism 5, 11, but may be fixed by means of a lever 46 and a wire 56. Further, the base frame 13 is provided with a slider 16 which may move outward through an opening 30 formed in the tiltable frame 27. When the base frame 13 is not fixed by the lever 46, the vertical arm 12 moves rearward in association with the extension of a cylinder 4, and then, the derricking arm 12 rotates. At this time, the slider 16 moves outward from the opening 30. When the base frame 13 is fixed by the lever 46, all arms rotate around a shaft 41 together with the tiltable frame 27.