The invention relates to a one-time flanging device for two ends of a tank body. The device comprises a rack, an input conveyer belt arranged on the rack and used for conveying the tank body, an output conveyer belt, a pair of holding devices for holding the tank body, and a pair of flanging dies for flanging the two ends of the tank body, wherein the pair of holding devices is arranged on the front side and the rear side of the tank body respectively; the pair of flanging dies is arranged on the left side and the right side of the tank body respectively; the input conveyer belt and the output conveyer belt are arranged on the upper side and the lower side of the flanging dies respectively; and the tank body falls between the flanging dies from the input conveyer belt to perform flanging,and the flanged tank body falls on the output conveyer belt. The device can effectively improve the capacity, ensure the quality of the flanged tank body, improve the flanging precision, play a good role in energy conservation and consumption reduction, reduce the labor intensity of personnel and remarkably improve the operation safety.