1. word latent topic estimation device for estimating a probabilistic word latent topic sequentially each time a document is added, comprising: a document data addition unit that inputs a document including one or more words; a level setting unit that sets the number of topics at each level in accordance with a hierarchical structure of topics for hierarchically estimating a latent topic of a word, the hierarchical structure constituted with a preset width and a preset depth; a higher-level constraint creation unit that creates a higher-level constraint for a word in the document on the basis of a result of topic estimation at a given level, the higher-level constraint indicating an identifier of a topic that is likely to be assigned to the word and the probability of the word being assigned to the topic; and a higher-level-constraint-attached topic estimation unit which, when estimating the probability of each word in the input document being assigned to each topic, refers to the higher-level constraint which is created by the higher-level constraint creation unit and uses the probability of the word being assigned to a parent topic at a higher level as a weight to perform estimation processing for a lower-level topic.