A search server includes a category database that stores category information containing location information indicating a geographical location, a word assigned to the location, and a user ID identifying a user having assigned the word to the location in association with one another, and a dictionary registration unit that reads first input information indicating locations to which a first word is assigned by a first user and second input information indicating locations to which a second word is assigned by a second user, and when determining that the first and second users have assigned the words to a predetermined number or more of common locations based on those information, creates dictionary data containing the first and second words in association with each other and enters the dictionary data into a dictionary database.