PURPOSE: To provide a Japanese analysis method by which the modification relation of clauses as against a long Japanese sentence where the number of the clauses is large is efficiently approved and the equivocal generation of modification can be made minimum.

CONSTITUTION: A morpheme analysis part 2 refers to a morpheme dictionary 5 and word-divides an input sentence so as to decide the clauses. A modification analysis part 3 refers to a modification dictionary 6 and extracts the collection of more than one clauses constituting a predicate clause. The predicate clause is classified stepwise in accordance with the strength of independency so that it is adjusted to the expression structure of Japanese, and the structure of the input sentence is analyzed based on the strength of the independency of the predicate clause. The modification relation of the respective clauses is approved on the input sentence which is structure-analyzed, and the structure of the Japanese input sentence is analyzed.