There are provided a system and method for tracing back an attacker by using centroid decomposition technique, the system including: a log data input module collecting log data of an intrusion alarm from an intrusion detection system; a centroid node detection module generating a shortest path tree by applying a shortest path algorithm to network router connection information collected by a network administration server, detecting a centroid node by applying centroid decomposition technique removing a leaf-node to the shortest path tree, and generating a centroid tree whose node of each level is the detected centroid node; and a traceback processing module requesting log data of a router matched with the node of each level of the centroid tree, and tracing back a router identical to the log data of the collected intrusion alarm as a router connected to a source of an attacker by comparing the log data of the router with the log data of the collected intrusion alarm. According to the system and method, an attacker causing a security intrusion event may be quickly detected, a load on the system is reduced, and a passage host exposed to a danger or having weaknesses may be easily recognized, thereby easily coping with an attack.