1. An intruder detection system comprising: a leaky transmission path of a transmission side, the leaky transmission path of the transmission side having a plurality of leaky points existing in a direction to which the leaky transmission path of the 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 that receives a leaky electric wave from the leaky transmission path of the transmission side, the leaky transmission path of the receiving side having a plurality of leaky points existing in a direction to which the leaky transmission path of the receiving side extends, wherein the leaky transmission path of the transmission side and the leaky transmission path of the receiving side form a detectable region therebetween for detecting an intruder, the detectable region including a detection area in which detection of an intruder is necessary and a non-detection area in which detection of an intruder is not necessary; a receiving circuit that receives signals respectively corresponding to leaky electric waves at the leaky points of the receiving side; an intrusion location detection unit that detects an intrusion location of an intruder within the detectable region, on the basis of whether one of the signals received by the receiving circuit indicates a variation of a corresponding one of the leaky electric waves at a corresponding one of the leaky points from which the one of the signals is received by the receiving circuit, and that outputs intrusion location information indicating the detected intrusion location of the intruder; a storage unit having stored therein a detection table in which a plurality of detectable intrusion locations within the detectable region are respectively defined in association with one of the detection area of the detectable region and the non-detection area of the detectable region, wherein at least one of said plurality of detectable intrusion locations within the detectable region is defined in the detection table as being within the detection area of the detectable region, and at least one other one of said plurality of detectable intrusion locations within the detectable region is defined in the detection table as being within the non-detection area of the detectable region; a processing unit that compares the intrusion location indicated in the intrusion location information output from the intrusion location detection unit with said plurality of detectable intrusion locations defined in the detection table to determine whether one of an intruder and a non-intruder is present in the intrusion location indicated in the intrusion location information output from the intrusion location detection unit, wherein the processing unit determines that an intruder is present in the intrusion location indicated in the intrusion location information when the intrusion location corresponds to the at least one of said detectable intrusion locations which is defined in the detection table as being within the detection area of the detectable region, and determines that a non-intruder is present in the intrusion location indicated in the intrusion location information when the intrusion location corresponds to the at least one other one of said detectable instruction locations which is defined in the detection table as being within the non-detection area of the detectable region; and a detection result output unit that outputs a detection result indicating the presence of the intruder in the detection area of the detectable region, when the processing unit determines that the intruder is present in the intrusion location indicated in the intrusion location information output from the intrusion location detection unit.