A threat detection apparatus and a threat detection method thereof for a wireless communication system are provided. The threat detection apparatus receives an observed time difference of arrival (OTDOA) message for positioning a user equipment (UE) from a serving base station (BS), and determines that the UE connects to a false BS when the identity of the serving BS is not on the identity list. If the identity of the serving BS is on the identity list, the threat detection apparatus calculates a first distance according to the measurement report message transmitted from the UE, and calculates a second distance between the UE and the serving BS according to the OTDOA message. When the difference between the first distance and the second distance is larger than a threshold, the threat detection apparatus determines that the UE connects to the false BS.