1. An intruder detection system comprising: a leaky transmission path of a transmission side, the leaky transmission path having a plurality of leaky points existing in a direction to which the leaky transmission path extends; a leaky transmission path of a receiving side that is provided together with the leaky transmission path of the transmission side and receives a leaky electric wave from the leaky transmission path of the transmission side, the leaky transmission path having a plurality of leaky points existing in a direction to which the leaky transmission path extends; an intrusion location detection unit which detects an intrusion location of an intruder on the basis of each signal, which is received in a receiving circuit of the receiving side, affected by the leaky electric wave at each of the leaky points; and a detection table that associates a detectable intrusion location with a detection area, wherein it is determined that an intruder is present when an electric wave received in the leaky transmission path of the receiving side varies, and if intrusion location detection information of the intrusion location detection unit corresponds to a detection area of the detection table, a detection result is output.