PURPOSE: To prevent an occurrence of defective printing at the time of printing by a printer and ensure a wide personal information printing area by a method wherein in a threefold sealed letter form for forming a sealed letter by peripherally bonding a sealed letter upper paper piece, a sealed letter intermediate paper piece, and a sealed letter lower paper piece which are folded in three, adhesives vertically applied on the top and rear surfaces thereof have a broken line form.

CONSTITUTION: In a threefold sealed letter form for forming a sealed letter by peripherally bonding a sealed letter upper paper piece A, a sealed letter intermediate paper piece B, and a sealed letter lower paper piece C which are folded in three at fold lines 5, adhesives 1', 2' out of adhesives for bonding the sealed letter paper pieces A-C at the peripheral parts thereof are applied in a broken line form on the top surface of the threefold sealed letter form. In addition, adhesives 11', 12' are applied in a broken line form on the rear surface of the threefold sealed letter form. As a result, a projected unevenness caused by the adhesive on the rear surface is prevented from occurring in an area of the paper pieces B, C on the top surface of the form. An occurrence of a defective printing is prevented at the time of printing by a prinbter. A large personal information printing area made of the paper pieces B, C on the top surface of the form is obtained.