The invention is to provide a method for manufacturing a joined sheet product. The method comprising a first joining step including opposing a transverse end face of a first sheet product(1) to a transverse end face of a second sheet product(2) and joining release films of the first and second sheet products with a first joining member(30); a removing step including removing a portion of an intended member including at least a surface protecting member so as to leave at least the release film and a pressure-sensitive adhesive provided on the release film among the constituent members of both or any one of the first and second sheet products(1, 2), wherein the portion has a predetermined length from the transverse end face of the intended member; and a second joining step including providing a second joining member(40) on at least an exposed portion(40b) resulting from the removal of the intended member to join the surface protecting member sides of the first and second sheet products(1, 2).