Provided is a fully automatic carton molding machine. The fully automatic carton molding machine comprises a rack, a transmission belt which is arranged on the rack and extends outward, a box pressing device which is arranged above the transmission melt, a box holding device which is arranged on two sides of the box pressing device, and a molding machine head device which is arranged below the transmission belt. The fully automatic carton molding machine further comprises a programmable logic controller (PLC) controlling system for controlling the transmission belt, the box pressing device, the box holding device, and the molding machine head device. The molding machine head device comprises four molding machine heads and the molding machine heads can independently complete molding work, so that the fully automatic carton molding machine is stable at work. Lifting-dropping barrel bodies are arranged on all the molding machine heads, the lifting-dropping barrel bodies can independently lift and drop, a shovel device and a plate pressing device of the molding machine heads can rotate and tilt, and thus the fully automatic carton molding machine is flexible at work. Due to the fact that the PLC controlling system for controlling is the transmission belt, the box pressing device, and the molding machine head device, automatic production is achieved, and thus production efficiency and product pass percent are improved.