The invention relates to the field of packaging equipment and particularly relates to a carton forming device comprising a rack and a base provided with a forming die; the forming die comprises a conveying belt as well as an inlet and an outlet which are respectively located at two ends of the conveying belt; each of two sides of the conveying belt is fixedly connected with a pre-folded plate; a cuboid core body fixedly connected with the rack is also arranged inside the forming die, and the spacing distance between the core body and the end, close to the outlet, of the forming die is 1-1.5mm; a hydraulic machine connected with the rack is arranged above the outlet; the lower end of the hydraulic machine is fixedly connected with a pressing block; the lower end of the pressing block is fixedly connected with a rubber bag filled with glue; the lower end of the rubber bag is provided with a nozzle communicating with the inside of the rubber bag; and the nozzle is provided with a pressure valve. By using the carton forming device, the problem of relatively low artificial folding efficiency can be solved.