A card forming sheet includes an opaque printing sheet and a transparent film placed over the printing sheet, so that the transparent film can be peeled away from the printing sheet and cannot be re-bonded to the printing sheet. Moreover, the card forming sheet includes a transparent adhesive and a peeling sheet placed over the adhesive layer. The printing sheet is divided into a substantially rectangular address describing part, an information describing part adjacent to one side of the address describing part, and a concealing part adjacent to another side of the address describing part. The card forming sheet is folded along a boundary between the address describing part and the information describing part. The two sides are bonded together so that the printing sheet is placed to the outside, and the card forming sheet is then folded along a boundary between the concealing part and the address describing part and bonded together, removably concealing the information.