To provide a roll media capable of discriminating whether the roll media supported by the media supply part of a printer is an adaptable one quickly without resorting to much procedures.

A radio tag 70 to record the media management information of the roll media 10 is attached to the core part 14 of the roll media supported by the media supply part 50 of the printer. The media management information recorded in the tag 70 is read by a reading means 90 to serve for discriminating whether the roll media 10 supported by the media supply part 50 is the adaptable one.