To provide a sealed letter openable into a booklet shape, capable of being manufactured by folding one letter paper piece to bond the peripheral edge thereof and forming an opening perforation at the peripheral edge.

The sealed letter 1 openable into a booklet shape comprises a letter paper piece wherein two rectangular page paper pieces are connected on the side of a long side and a plurality of rectangular page paper pieces are connected on the side of a short side and a seal paper piece 17 is connected to the long sides of the page paper pieces of one end edge. In this letter paper piece, the page paper pieces are turned and folded from end edges, to which no seal paper piece 17 is connected, along short side fold lines to be bonded along a long side fold line and the turned and folded letter paper piece are folded double along the long side fold line and the page paper pieces are bonded along the short sides of the folded letter paper piece and the seal paper piece is folded to be bonded to the opposed page paper pieces and opening perforations 2a, 2b and 2c are formed along both short sides of the folded letter paper piece and the long side to which the seal paper piece is connected.