To provide a sealing letter form which can be printed by using a general-purpose printer and can be sealed without using a special machine.

The sealing letter form (8) comprises a first base and a second base which are laminated via an adhesive layer applied on their entire surfaces. An address indication section is provided on at least a part of a surface (9) of an adhesive sheet of the form, and an information indication section is also provided on at least a part of a surface (10) of release paper of the form. A cutting line (12) extending along one of sides of the release paper is further provided on the side. The letter form (8) is folded with a side of the cutting line left, a part (13) of the release paper surrounded by the cutting line is removed, and a part of the adhesive layer exposed by the removal is glued to the surface of the opposite adhesive sheet by folding the form (8), whereby the form is sealed.