At a top face of a substantially parallelepipedic package, plate members having cutting blades at side edges thereof are inserted into a gap between a pair of bonded flaps of packaging material on the one hand and, on the other, packaged items and folded edges of the packaging material to cut the packaging material along the edges of the top face. The cut portions of the packaging material are opened with suction pads, and holding members of an unloader are inserted into two ends of the package from the opened top face to hold and take out the packaged items.