To provide an unloading device and a truck, integrally and stably moving a moving plate and a pressing member at the time of outward movement in unloading work, and simplifying an oil pressure circuit to be formed, and performing unloading work at good work efficiency.

This unloading device is so constructed that when pressure oil is supplied to a cylinder mechanism 7 for a moving plate to move the moving plate 2 in the outward direction, pressure holding is performed by a pressure holding means 49 to move the pressing member 4 in the outward direction along with the moving plate 2. This unloading device is provided with the pressure holding means 49 for holding the pressure to bring a lock member 87 into pressure contact with a side wall member 3 in the state of stopping the supply of pressure oil after the pressure oil is supplied to a locking cylinder mechanism 88. This unloading device is adapted to supply oil pressure to the locking cylinder mechanism 88 as well when the oil pressure is supplied to the moving plate cylinder mechanism 7 to move the moving plate 2 in the returning direction.