To provide a tilting device for a truck for carrying and discharging earth and sand on tunneling work with a simple structure and at a low cost capable of preventing breakdown and repairable easily in a case of breakdown.

This tilting device 40 includes an air bag 36 expanding under a pressure of air. The air bag 36 is provided on the lower side of a bottom surface of a truck body 12. The air bag 36 in a flat state is expanded and the bottom surface of the truck body 12 is pushed up. Then, the truck body 12 is tilted around a support shaft 22 to discharge earth and sand in the truck body 12 to the outside.