An intrusion detection system and method of a wireless network providing wireless communication to one or more wireless terminal, and an intrusion detection sensor capable of detecting attacks against wireless network are provided. The intrusion detection system of a wireless network includes: an access point providing wireless communication to a wireless terminal; and an intrusion detection sensor examining packets transmitted and received between the access point and a wireless terminal according to a predetermined detection rule. The access point transmits confirmation information on whether or not an event packet, including critical information on whether or not a wireless line connection between the access point and the wireless terminal is established, is transmitted, to the intrusion detection sensor, and the intrusion detection sensor examines an event packet by using the confirmation information. According to the system and method, a variety of attacks occurring on a wireless network can be effectively detected and systematically controlled.