A plastic bag sealing device includes a work table, a sealing device having a silicon rubber roller, a material intake press roller and a material outlet press roller fixed beside the silicon rubber roller to press thereon, plural rotating shafts fixed outside around the silicon rubber roller and respectively mounted with a sealing blade, plural guide rollers employed to conduct plastic bags, a dot-cutting device, an opening-cutting device, and a press roller fixed beside the dot-cutting device and the opening-cutting device. With the sealing blades to carry out multiple sealing at the same location, a plastic bag can be quickly and firmly sealed, and with the dot-cutting device and the opening-cutting device installed on the work table to respectively execute dot-cutting and opening-cutting, the work table can be comparatively downsized, thus greatly elevating economic gain.