The wrist watch with internal tag according to the present invention includes a watch case 12 which includes a ring shaped case 12a and a rear lid 12c, a drive section 13 which is housed in the watch case, a display section 14 which is housed in the watch case 12, is driven by the drive section 13, and displays a time instant, and an RFID tag (18) which is housed in the watch case 12 and includes an antenna 16 and an IC chip 17. The antenna includes a rod shaped magnetic core member 16a which is provided to follow around the inner surface of the rear lid 12c between the ring shaped case 12a and the drive section 13, and a coil 16b which is wound in a helical shape around the magnetic core member 16a. And the magnetic core member 16a is shaped so as to bend around following the inner surface of the ring shaped case (12a), and is made from a layered amorphous foil material or a composite material so as to have a certain flexibility.