To provide a reply-paid envelope capable of being used as a sending envelope and a reply envelope with a single sheet, and to provide a method for using the same.

The reply-paid envelope includes: an envelope having a reply address information described on a surface, a sending address information described on the back surface, and a flap mounted in an opening; and a re-peelable label on which a re-peelable adhesive agent enabling a plurality of repetitions of pasting and peeling the label is applied. The label is an connection label of an address label piece on which the sending address information is described, a pay method description label piece for sending, and a sealing label piece sealing the opening of the envelope, these piece being connected via perforations. The sealing label piece is larger than the flap. The sum of the surface areas of the address label piece and a charge display piece is larger than the description range of the reply address information and the charge pay method described on the surface of the envelope. The address label piece and the charge display label piece among the labels are pasted on the surface of the envelope to conceal the description of the reply address information and the charge pay method.