PURPOSE: To retrieve the word from significance by executing a collation by containing similarity of each predicate and case of a semantic structure network of an inputted sentence and a semantic structure network of semantics of a keyword of a dictionary and outputting a coincident keyword.

CONSTITUTION: A syntax analyzing part 1 generates a semantic structure network by executing a syntax analysis of an inputted input sentence, a semantic structure network 3 is a semantic structure network generated by executing a syntax analysis of semantics of a keyword of a dictionary, and a semantics collating part 4 executes a collation with the semantic structure network 3 generated from the dictionary with regard to the predicate and the case, and also, a similar one in the semantic structure network generated from the input sentence by the syntax analyzing part 1. In this case, the syntax analyzing part 1 executes the syntax analysis of the inputted input sentence and generates the semantic structure network, and with regard to its predicate and case, a collation is executed by containing similarity with the semantic structure network 3 generated from the dictionary, and the keyword of that which is subjected to matching is outputted. In such a way, a word of the dictionary can be retrieved from significance.