A full-automatic bag making machine comprises a forming device, a buffering device, a cutting device, a steering device, a sewing device and a bottom wrapping device. Planar cloth can be bent, glued and formed into cylindrical cloth by means of the forming device. The buffering device is connected behind the forming device, can guide the cylindrical cloth to enter and can control the front-back conveying speed of the cylindrical cloth. The cutting device is arranged behind the buffering device so that the cylindrical cloth can be cut into a plurality of through cylindrical bags. The steering device comprises a conveying machine table which is arranged behind the cutting device and can change the conveying direction of the cylindrical bags and bend the cylindrical bags by 90 degrees. The sewing device is arranged on one side of the conveying machine table so that the bottom edges of the cylindrical bags can be sewn and sealed. The bottom wrapping device is arranged outside the conveying machine table so that the bottom edge of each cylindrical bag can be wrapped and sealed by a sealing belt. The function of manufacturing the planar cloth into the complete cylindrical bag finished products in a full-automatic mode is achieved by means of the buffering device.