PURPOSE: To provide an information concealing postcard concealing and transmitting information, which is unwilling to be known by others, or secret information.

CONSTITUTION: A plurality of sheets are folded and at least one set of sheets are stuck peelably together. Since an auxiliary piece 3 is formed on a side part running along the opposite side of a folding machine 2d of one side out of the one set of the sheets through a folding line 2f and the auxiliary piece 3 is folded back to the surface opposite to a peeling surface of the sheet for adhesion, it is prevented from being opened erroneously during mailing, pseudo adhesive surface is peeled off by cutting off a prearranged part of cutting after receipt and concealed information can be confirmed visually.