The invention relates to a packing machine which comprises a framework, a film supply device, a film feeding device, a feeding hopper, a plurality of collar forming devices, a horizontal sealing device, a plurality of vertical sealing devices, a slitting device, a detection device and a separation device. The horizontal sealing device comprises two upright guide rails, two sliders, two cylinders, two touch cylinders, front pressing pieces, rear pressing pieces and a support, and the two sliders are matched with the guide rails; the two sliders are respectively mounted on the two guide rails, and inner sides of the two sliders are fixedly connected with the support; outer sides of the two sliders are respectively connected with telescopic arms of the two cylinders, the front pressing pieces are fixedly mounted on telescopic arms of the two touch cylinders, and the two touch cylinders are fixedly mounted on the front side of the support. The packing machine in a multi-column design has the advantages that the production efficiency is greatly improved, a mechanical structure is simplified, and the product percent of pass is guaranteed owing to the additional detection device and the additional separation device.