To establish the cold keeping or warm keeping effect for the loaded object and also the odor dispersion preventive effect to a certain degree only by furnishing a dump truck rear body with a plurality of opening/closing members and a driving power source for them.

When an object loaded on the rear body 4 of a dump truck is dropped, the second opening/closing member 6 makes opening movement so as to overlap on one side face of the first opening/closing member 5 while the second member 6 is guided by the first opening/closing member 5 by the drive force of the second driving force source 55 furnished on the first opening/closing member 5 and opens the rear of the over-opening 18 of the rear body. When an object is loaded on the rear body 4, the first opening/closing member 5 together with the overlapping second opening/ closing member 6 opens fully the over-opening 18 of the rear body 4 through a left and a right movable long rod 26 moving to over the upper wall surface of the driver cab and the first opening/closing plate 27 fixed to the long rods in the form of a roof while it 5 is guided in engagement by a guide engaging part 20 formed on the side wall by the driving force of the first driving force source 50 furnished fast on at least either of the left and right side walls 7.