Abstract: A fastening device includes a cylindrical shell with an opening extending over the entire length of the cylindrical shell, a gripping member formed on the periphery of the cylindrical shell by extending outward and a pair of hooks linked with the tip end of the cylindrical shell via hinges. A fastening method using the foregoing fastening device includes the steps of passing the pair of hooks through a hole for fastening of a packing box formed of an upper box and a lower box, having the pair of hooks opened outward to bring the holding members thereof into contact with the back side surface of the packing box and at the same time having the pair of hooks engaged with each other firmly. At this time, the gripping member is in contact with the front side surface of the packing box. Accordingly, both surfaces located at each respective rim of the hole for fastening are sandwiched between the pair of hooks and the gripping member.