An information retrieval apparatus using a preference-based association dictionary, having words stored therein that are dynamically changed according to user's preferences, and using a general association dictionary storing a relationship between keywords included in a database. The apparatus includes: a matching unit which calculates a degree of matching between a search condition inputted from an input unit and a profile; a generation unit which obtains (i) one or more related words from a general association dictionary in a case where the matching degree is smaller than a predetermined threshold, and (ii) one or more related words from a preference-based association dictionary in a case where the matching degree is greater than the predetermined threshold; and a retrieval unit which retrieves information that meets the generated search condition.