9. An information association apparatus according to claim 8 further comprising: said association degree dictionary composed of an interval association degree dictionary which stores the correlation degree of key words found by calculating the association degree between said two key words based on the minimum time interval which is the smallest value among time intervals during which each query extracted for each search user was used from the queries used during the past predetermined period, and adding said association degrees calculated for a plurality of said search users, and a correlation degree dictionary which stores the correlation degrees for key words found by compiling said queries for each user for each predetermined time interval from queries used during said past predetermined time interval, calculating for each of said users the number of uses of key words among said queries within said predetermined time interval, adding said number of uses of each key word for all of said search users, and calculating the association degree between two key words based on the number of uses of each of said key words, and further characterized by: said initialization unit which generates initial groups for grouping key words according to the interval association degree and the correlation degree stored in said interval association degree dictionary, and said grouping unit grouping associated key words by sequentially making groups satisfying predetermined conditions into one group using said initial groups and the interval association degree between key words stored in said interval association degree dictionary and the correlation degree between key words stored in said correlation degree dictionary.
9. An information association apparatus according to claim 8 further comprising: said association degree dictionary composed of an interval association degree dictionary which stores the correlation degree of key words found by calculating the association degree between said two key words based on the minimum time interval which is the smallest value among time intervals during which each query extracted for each search user was used from the queries used during the past predetermined period, and adding said association degrees calculated for a plurality of said search users, and a correlation degree dictionary which stores the correlation degrees for key words found by compiling said queries for each user for each predetermined time interval from queries used during said past predetermined time interval, calculating for each of said users the number of uses of key words among said queries within said predetermined time interval, adding said number of uses of each key word for all of said search users, and calculating the association degree between two key words based on the number of uses of each of said key words, and further characterized by: said initialization unit which generates initial groups for grouping key words according to the interval association degree and the correlation degree stored in said interval association degree dictionary, and said grouping unit grouping associated key words by sequentially making groups satisfying predetermined conditions into one group using said initial groups and the interval association degree between key words stored in said interval association degree dictionary and the correlation degree between key words stored in said correlation degree dictionary. 10. An information associating apparatus according to claim 9 wherein: said initialization unit generates each group including one different key word stored in said association degree dictionary, as said initial groups.