An active tag device includes a controller to cause the wireless communication unit to carry out data transmission at intervals of a first period, and to cause to start measurement of a second period set for determining a timing for causing a wireless communication unit to carry out carrier sense to detect data output by a reading writing apparatus, synchronously with the data transmission, and to cause the wireless communication unit to carry out the carrier sense after the second period elapsed. The reading writing apparatus includes a controller to cause to start measurement of the first period set for synchronizing with carrier sense of the active tag device after a wireless communication unit detected reception of data from the active tag device, and to cause the wireless communication unit to carry out data transmission to the active tag device during the second period after the first period elapsed.