An active contactless information storage device includes: an operation controller that determines whether mode information of the active contactless information storage device indicates a mode in which the device communicates with a reader/writer device; a carrier-sense controller that determines whether a first frequency in a first period and determines whether a second frequency in a second period, when the mode information of the active contactless information storage device indicates the mode in which the device communicates with the reader/writer device; and a command processor that performs communication with the reader/writer device when the carrier sense controller determines that the first frequency is sensed; wherein, when the mode information of the active contactless information storage device does not indicate the mode in which the active contactless information storage device communicates with the reader/writer device, the carrier-sense controller waits for a predetermined amount of time.