To provide a document retrieval processor for accurately grasping the characteristics of a document group acquired as a retrieval result by checking whether or not the combination of a plurality of words arbitrarily selected by each user is included in a plurality of documents to be retrieved at the same time.

A document retrieval processing part 101 of a document retrieving system 100 includes a frequency calculation processing part 104 for calculating the frequency of keywords and relevant keywords included in a document acquired as a retrieval result, and the retrieval result and each frequency calculation result are displayed at a Web page 110. Regarding the combination of keywords arbitrarily selected by each user, a relevant keyword registration processing part 103 accepts a registration request as a relevant keyword, and stores it in a relevant keyword database 109.