PURPOSE: To improve the cost deciding accuracy and percentage of correctness of the maximum likelihood solution by deciding a maximum likelihood morpheme sequence from the total sum of node and arc costs.

CONSTITUTION: An analyzing section 2 analyzes a Japanese sentence inputted from a sentence inputting device 1 by using the dictionary and connection tables of a dictionary/connection table 3 and obtains a solution. A cost deciding section 4 decides the cost of the solution obtained by the section 2 by referring to a cost deciding rule 5. A most likelihood solution selecting section 6 selects the solution of the lowest cost and a result outputting section 7 outputs the solution of the lowest cost selected by the 6 to a grammatical construction analyzing section. Since the maximum likelihood morpheme sequence is decided from the total sum of node and arc costs by also giving a cost to an arc which is a combination of morphemes in such way, the cost deciding accuracy and the percentage of correctness of the maximum likelihood solution are improved at the time of analyzing a morpheme.