A dump vehicle overturn preventing device includes: a loaded weight estimation unit which estimates loaded weight on the body; a vehicle rotation moment calculation unit which calculates a vehicle rotation moment Mb caused by movement of the dump vehicle's load upon discharging of the load; a reference moment calculation unit which determines a reference moment Ms not greater than an overturn threshold moment MI which is the minimum value of a rotation moment required to lift the front wheels off the ground; a judgment unit which judges whether or not the vehicle rotation moment Mb has exceeded the reference moment Ms; and a display device which notifies the driver that there is a probability of an overturn of the vehicle when the vehicle rotation moment Mb is judged to have exceeded the reference moment Ms.