1. A dictionary generation device comprising: a determination unit configured to (A) refer to an item database that stores a plurality of records containing an item name and/or item description including a noun, a noun phrase or a noun sequence being a sequence of nouns or noun phrases, an item category, and a shop selling the item as fields and determine whether the noun sequence included in the item name and/or item description of each record is set corresponding to the item category, (B) count the number of selling shops in a record containing the noun sequence set corresponding to the item category for each item category and calculate a shop intensity of each noun sequence set corresponding to the item category based on the counted number of selling shops, (C) determine whether one item category uniquely derived from the noun sequence exists based on the shop intensity for each item category, and (D) determine the noun sequence as a definitive category word when the one item category exists; and a registration unit configured to store dictionary information where the definitive category word and the uniquely derived item category are associated with each other into a dictionary database.