To provide an ADS-B ground station improving reliability of acquired ADS-B monitoring information while restraining an increase in a device scale.

A mode S individual question of requesting DBS is made to an aircraft of newly making track information based on a received ADS-B signal, just after making this track information, and whether or not respective DBC in this newly made track information and a mode S individual response coincide with distance information after receiving and decoding its response signal. When these coincide, an aircraft of issuing the ADS-B signal and an aircraft responding to the mode S individual question are regarded as the same aircraft, and this is treated as an actual target, and this newly made track information is continuously held. While, when these do not coincide, this is regarded as an erroneous target, and the mixed presence of the erroneous target is reduced by abandoning this newly made track information.