To include not only much amount of information printed by a printer, but also additional papers other than the information and a stamped, self- addressed envelope if necessary by a method wherein a glue pattern is added to a unit type sealing form while a plurality of sheets of sealing forms are superposed and folded to apply bonding work.

Sealing patterns G5, G6 are applied on the surfaces of first and second sheets of a sealing form other than a glue pattern G1, then, the first and second sheets are superposed whereby the glue patterns G2, G3, G4 are superposed on the same G5, G6, G7 respectively. Thereafter, the superposed sheets are folded into three plies and bonding work is applied whereby a sealing mail, produced by bonding both side surfaces of two sheets of sealing forms, can be obtained. A sealed composite type sealing mail is opened by bending perforated lines 1 at both side ends of the same to cut and separate them. According to this method, the composite type sealing mail can be produced easily and the mail is not separated into pieces when the same is opened whereby the mail can be kept as one set of documents.