To provide an envelope whose cut off area is easily cut and separated.

The envelope 1 includes a bag shaped body 2 at least on one side of which an opening 3 is formed for placing therethrough a mail article, etc., a cover piece 4 for sealing the opening 3 being extended from the body 2, a folding line part 5 structured along the opening 3 and formed on the border between the body 2 and the piece 4, a cotton thread 6 internally mounted along the folding line part 5, a roughly circular cut/separate area 7 which is formed separably roughly at the center of the line part 5 and covers the body 2 and the piece 4, an adhesive tape 10 mounted on the piece 4 for attaching the body 2 and the piece 4, and a separation sheet 11 mounted on the tape 10 for protecting the tape 10.