A text analysis device includes a storage unit configured to store opinions of users who participate in a discussion about a predetermined theme as text data and author information for specifying authors of the text data, a feature quantity data generation unit configured to generate feature quantity data of the text data stored in the storage unit, an observation time-series signal generation unit configured to generate observation time-series signals based on information obtained by performing a predetermined process with respect to the feature quantity data, a change point detection unit configured to detect a change point of the discussion based on the observation time-series signals, and an influence specifying unit configured to specify an opinion having influence on an opinion corresponding to the specified text data out of opinions of the discussion based on the detected change point and the author information.