A cutting device of an integrated paper-plastic bag cutting and sealing machine includes a sliding bracket and a cutting knife. The sliding bracket is connected to a horizontal displacement driving mechanism. The sliding bracket is formed by connecting an upper plate with a rear plate. The sliding block is mounted on the rear plate through a connecting shaft and is capable of sliding back and forth along the connecting shaft, front and rear snapping grooves are arranged on the connecting shaft along the length direction. A cutting knife is mounted on the sliding block, its lowest position is lower than the bottom surface of the sliding block. A spring positioning column is mounted on the sliding block, the top end of the spring positioning column passes through the shaft hole wall of the connecting shaft of the sliding block and tightly presses against the connecting shaft.