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 extracts one or more intention estimation units each of which is a unit on which an estimation of said intention is to be performed from said inputted language; an intention estimator that estimates a partial intention which is an intention of a part which constructs each of the intention estimation units extracted by said intention estimation unit extractor from said each of the intention estimation units; and an intention co-occurrence weight calculator that calculates an intention co-occurrence weight based on a relationship between said partial intentions estimated by said intention estimator, wherein said intention estimating device includes 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 an intention co-occurrence weight which said intention co-occurrence weight calculator calculates for said partial intentions which construct said generated intention sequence.