To unseal an envelope, etc., easily and quickly without using a tool such as scissors and a knife, and moreover unseal the envelope, etc, cleanly without producing any cut pieces.

An envelope A comprises an envelope main body 1 having an opening and a flap 2 provided in a foldable manner on the side of the opening of the envelope main body 1. A peel-upeprimer layer 3 is formed on an inner face of an edge 2a of the flap 2. A solution or an emulsion, both containing a small amount of wax, etc., is preferable as a peel-up-primer forming the peel-up-primer layer 3. An adhesive layer 4 is formed in the form of a dotted line (in the form of a perforated line) on the surface of the peel-upeprimer layer 3. An adhesive forming the adhesive layer 4 may be any kinds of adhesives which are used by being wetted with moisture.