An apparatus for constructing Aho-Corasick automata according to the present invention includes a concatenative normal form transforming unit configured to receive a regular expression that is expressed using an operator including a concatenation and an alternation and transform the regular expression into concatenative normal forms (wherein each concatenative normal form is defined as a form in which character alternations are connected by concatenation); a trie generating unit configured to generate a trie from the concatenative normal forms by updating states and transitions of the trie (wherein each transition corresponds to a set of characters) while processing each concatenative normal form in order; and a failure link creating unit configured to create a failure link for each state of the trie by using a set of characters corresponding to each transition of the trie.