To provide a printer which can surely write information in the memory of one of a plurality of continuous RFID print media, even if the RFID print medium to be printed has various sizes.

This printer comprises: an input means which is used to input printing contents and information; a printing means for doing printing on the print medium on the basis of the printing contents which are input by the input means; radio communication means 21-25 which supply energy to an RFID and perform radio communication with the RFID, by transmitting a radio signal to the RFID, so as to store the information, input by the input means, into the RFID; and a transmission range switching means 26 for switching the strength of the radio signal, transmitted from the radio communication means, to any one of a plurality of levels.