A packaging box sheet assembled to obtain an affixed box comprising: a sheet-like mounting board; and a decorative paper disposed on the outer surface of the mounting board; wherein the mounting board includes: a bottom board whose outer periphery is a polygonal shape when viewed in a plan view; and a plurality of first side boards and a plurality of second side boards respectively connected to two sides sharing one apex at the outer periphery of the bottom board; wherein the decorative paper includes: a first paper portion affixed to the bottom board and the plurality of first side boards in advance; a second paper portion which corresponds to the plurality of second side boards, where the second paper portion is connected to the first paper portion, and where the second paper portion is not affixed to and is separated from the plurality of second side boards; and a third paper portion which is connected to the first paper portion and where the third paper portion projects from one side of the plurality of first side boards toward the plurality of second side boards (12b; and wherein the second paper portion and the third paper portion respectively have an adhesive layer and a release paper covering the adhesive layer. a sheet-like mounting board; and a decorative paper disposed on the outer surface of the mounting board; wherein the mounting board includes: a bottom board whose outer periphery is a polygonal shape when viewed in a plan view; and a plurality of first side boards and a plurality of second side boards respectively connected to two sides sharing one apex at the outer periphery of the bottom board; a bottom board whose outer periphery is a polygonal shape when viewed in a plan view; and a plurality of first side boards and a plurality of second side boards respectively connected to two sides sharing one apex at the outer periphery of the bottom board; wherein the decorative paper includes: a first paper portion affixed to the bottom board and the plurality of first side boards in advance; a second paper portion which corresponds to the plurality of second side boards, where the second paper portion is connected to the first paper portion, and where the second paper portion is not affixed to and is separated from the plurality of second side boards; and a third paper portion which is connected to the first paper portion and where the third paper portion projects from one side of the plurality of first side boards toward the plurality of second side boards (12b; and a first paper portion affixed to the bottom board and the plurality of first side boards in advance; a second paper portion which corresponds to the plurality of second side boards, where the second paper portion is connected to the first paper portion, and where the second paper portion is not affixed to and is separated from the plurality of second side boards; and a third paper portion which is connected to the first paper portion and where the third paper portion projects from one side of the plurality of first side boards toward the plurality of second side boards (12b; and wherein the second paper portion and the third paper portion respectively have an adhesive layer and a release paper covering the adhesive layer.