1. An intention estimating device that estimates a user's intention from the user's language input, said intention estimating device comprising: an intention estimation unit extractor that splits the inputted language into a plurality of morphemes and extracts, from the morphemes, one or more intention estimation units each of which is a unit on which an estimation of said intention is to be performed, each of the intention estimation units consisting of one or more morphemes; an intention estimator that estimates a respective partial intention which indicates a respective intention for each of the intention estimation units extracted by said intention estimation unit extractor; an intention co-occurrence weight calculator that calculates an intention co-occurrence weight having a value which depends on a relationship between said partial intentions estimated by said intention estimator; and an intention sequence estimator that: generates an intention sequence corresponding to said inputted language by using one or more said partial intentions estimated by said intention estimator, and generates an intention estimation result corresponding to said inputted language by using both a score showing a likelihood of said generated intention sequence and the intention co-occurrence weight calculated for said partial intentions which construct said generated intention sequence.