Provided is an apparatus for detecting a network attack situation. The apparatus includes an alarm receiver receiving a plurality of alarms raised in a network to which the alarm receiver is connected, converting the alarms into predetermined alarm data, and outputting the alarm data; an alarm processor analyzing an attack situation in the network based on attributes of the alarm data and a number of times that the alarm data is generated; a memory storing basic data needed to analyze the state of the network and providing the basic data to the alarm processor; and an interface transmitting the result of the analysis by the alarm processor to an external device, receiving a predetermined critical value from the external device, which is a basis for determining the occurrence of the attack situation, and outputting the critical value to the alarm processor such that the alarm processor can store the critical value in the memory. Equal numbers of hash engines and detection engines for processing the alarms in the network to the number of data groups classified as network attack situations are formed in a line. Therefore, a network attack situation can be detected in real time based on a great number of alarms indicating intrusion detection.