The invention wherein the middle deck (10,50 to be installed between the middle deck 10 and the front deck 20 of the central front lower the deck 20 with the middle deck (10,50) of the upper and lower layer W ), one end W supplied to the falling middle lifting unit 60 and the front deck (front lifting unit (70) and elevating the other end of the middle deck 50 of the upper layer for elevating the other end of the 20) of the a vehicle transport trailers (1) having a vehicle load deck, the lifting structure improvement, including the rear lifting unit (80) for, the middle deck 50 of the upper layer is the middle lifting unit 60 and a rear lifting unit ( 80), the middle deck ends of the upper layer by a driving means mounted to have been elevating at the same time, the middle deck 10 of the lower layer is elevating by a cylinder 68 mounted in the middle, lifting unit (60) on one side , and the other end is fixed to the rotatable cylinder to the trailer floor 100 By being configured such that at the same time elevating way, elevating the upper layer of the forward deck and middle deck and a lower layer of the middle deck a plurality of cylinders mounted to one of the lifting unit and securely fixed pin operated by a cylinder provided in the bottom deck position fixed to the lifting unit than the simplified structure and to reduce the production cost, there is an effect that the operation can be easy to perform a loading work vehicle more efficiently.