Provided is a heat sealer comprising: a base bar equipped with a heater on a receiving section; and a pressure bonding lever facing the receiving section and capable of pressing and holding a sealing portion of a resin made sealing preform to accommodate contents therein, and the sealing portion of the resin made sealing preform placed on the receiving section and pressed by the pressure bonding lever to the receiving section side to hold the sealing portion between the receiving section and the pressure bonding lever, and current-heated and weld-sealed, wherein the base bar comprises: a recording medium supplier supplying a recording medium from which specific information can be read to a predetermined position; and a recording medium transport machine transporting the recording media having been supplied to the predetermined position one at a time to the sealing portion, thereby the recording medium is sealable integrally with the sealing preform in a single piece.