Abstract: Apparatus mounted on a self-propelled truck, and provided with mechanisms for effectively, smoothly, and safely performing various timbering work in drift and tunnel walls and roofs. The mechanism includes a working platform which is rotatable and kept horizontal for easy conveyance of timbering materials even in a narrow drift and for steady performance of timbering by workers on the platform. Planting of props is readily performed by a device provided to the platform, which grasps a prop, shifts it and erects the prop over a selected pit, and bridging of top beams over capitals of planted props is accurately made by lifting means provided on the working platform.