1. The related-word registration device comprising: a receiving means that receives a search query of a search word entered by the user; a search query storing means that stores the received search queries in accordance with reception order; a search query extracting means that extracts, from the search query storing means, a preceding search query whose reception order is earlier than that of the received search query on the basis of a preset search query extracting condition; a character string set storing means that stores, as a character string set, a preceding search word constructing the extracted preceding search query and a search word constructing the received search query; a character string extracting means that extracts a character string set having the search word which is the same or similar to the preceding search word from the character string set storing means in accordance with a preset character string set extraction start condition; a related-word specifying means that specifies a character set as a related word from the extracted character string set on the basis of a preset registration condition; and a related-word registering means that registers the specified character string set as related words into a related-word database.
1. The related-word registration device comprising: a receiving means that receives a search query of a search word entered by the user; a search query storing means that stores the received search queries in accordance with reception order; a search query extracting means that extracts, from the search query storing means, a preceding search query whose reception order is earlier than that of the received search query on the basis of a preset search query extracting condition; a character string set storing means that stores, as a character string set, a preceding search word constructing the extracted preceding search query and a search word constructing the received search query; a character string extracting means that extracts a character string set having the search word which is the same or similar to the preceding search word from the character string set storing means in accordance with a preset character string set extraction start condition; a related-word specifying means that specifies a character set as a related word from the extracted character string set on the basis of a preset registration condition; and a related-word registering means that registers the specified character string set as related words into a related-word database. 2. The related-word registration device according to claim 1 , wherein the search query storing means further stores user identification information, and the search query extracting means extracts the preceding search query whose user identification information matches that of the user who entered the search query as the search query extraction condition.