Provided is an overturn preventing device for a dump vehicle equipped with a body (3) and hoist cylinders (5). The dump vehicle overturn preventing device comprises: a loaded weight estimation unit (32) which estimates loaded weight on the body; a vehicle rotation moment calculation unit (33) 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 (34) 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 (1) off the ground; a judgment unit (35) which judges whether or not the vehicle rotation moment Mb has exceeded the reference moment Ms; and a display device (37) 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. The device thus prevents overturning of the vehicle caused by the load sliding down from the body in a lump.