Disclosed is a dumping work determination system for a haulage vehicle provided with a body frame, a vessel and a drive mechanism for selective raising or lowering of the vessel. The system is applicable to the vehicle to determine a state of loading in the vessel in dumping work, and includes a body frame speed detector, a tilted state detector, a shake detector, and a payload-stuck state determination unit. Based on signals from the detectors, the unit determines whether or not the state of loading is a payload-stuck state. Specifically, the unit determines the payload-stuck state when the speed of the body frame is detected to have reached lower than a predetermined speed, the vessel is detected to have tilted to a predetermined position, and a state where the vessel can be considered to have no longer produced shakes is detected by the shake detector.