To enlarge a recording face of an enclosed sheet, located in the window of an envelope, and to magnify the recording face of the enclosed sheet.

In the structure of the envelope having the window through which descriptions such as the postal code, the address, the name, and the telephone number of the receiver of an electricity bill transfer paper 5 are visible from outside, a magnifier 2 for magnifying images is attached to the window 1 made in the surface 20 of the main body of the envelope 8. Perforations 3 are formed around the window 1 in the main body 8 of the envelope so that the magnifier 2 can be detached from it.