A network intrusion detection apparatus and method that perform Perl Compatible Regular Expressions (PCRE)-based pattern matching on the payloads of packets using a network processor equipped with a Deterministic Finite Automata (DFA) engine. The network intrusion detection apparatus includes a network processor core for receiving packets from a network, and transmitting payloads of the received packets to a Deterministic Finite Automata (DFA) engine. A detection rule converter converts a PCRE-based detection rule, preset to detect an attack packet, into a detection rule including a pattern to which only PCRE grammar corresponding to the DFA engine is applied. The DFA engine performs PCRE pattern matching on the payloads of the packets based on the detection rule converted by the detection rule converter.