Abstract: A secret postcard in accordance with the present invention is comprised of a single sheet, and a released paper. The sheet is foldable about a return line, and has a first area and a second area. A first perforation, and a second perforation are formed at a front surface of the second area. A first adhesive layer is formed at a rear surface of the second area in an area sandwiched between the return line and the first perforation. A second adhesive layer is formed at the rear surface of the second area in an area sandwiched between the second perforation and an edge of the second area extending in parallel with the return line. The second adhesive layer has such an adhesive force that the rear surfaces of the first and second areas cannot be released from each other after they were adhered to each other.