1. A packet classification apparatus using a field level tries structure, said apparatus comprising: a main processing part for generating and maintaining the field level tries structure, which organizes a multi-field packet by field in a hierarchical structure for classifications; and a plurality of classification engines, each classification engine provided with a first classification part for performing queries and updates and processing a prefix lookup represented by an IP address lookup, and a second classification part for proceeding with packet classification by field based on a result of the first classification part in order to process a range lookup belonging to the result.