The invention discloses a bag making machine. According to the technical scheme, the bag making machine is mainly characterized by comprising a rack, the rack is provided with a feeding device for feeding plastic film rolls and a heat-sealing device, the heat-sealing device comprises heat-sealing knives, the two heat-sealing knives are parallel to each other, and a cutting device for cutting a plastic film is arranged at the position, located at the downstream of the heat-sealing device, of the rack; the bag making machine is provided with the two heat-sealing knives and the cutting device, and the heat-sealing knives only play a role in sealing the plastic film instead of cutting the plastic film, so that after heat-sealing of the plastic film is completed, a pair of parallel heat-sealing strips are formed on the plastic film, then the plastic film is sent into the cutting device, the cut position of the cutting device is located between the two heat-sealing strips, thereby the structures of the heat-sealing strips cannot be damaged, sealing performance of a plastic film bag cannot be influenced, the plastic film is not separated through heat cutting, stringing cannot be generated, and product quality and hand feeling of users in the later-stage using process are improved.