To provide a two division search/retrieval device which can retrieve a dictionary at higher speed through the use of a binary search index whose size is small.

Indexes and corresponding information are stored in a data storage part 101 in the order of the Japanese syllabary, for example. A retrieval range update part 111 sets the retrieval word of the maximum order in the Japanese syllabary to be a retrieval object in the retrieval word group which is not retrieved yet and updates a retrieval range with the binary search until the retrieval range for the pertinent retrieval word becomes prescribed retrieval width. A retrieval part 114 retrieves the pertinent retrieval word on all the indexes in the pertinent retrieval range so as to terminate the binary search/ retrieval for the pertinent retrieval word after update by the retrieval range update part 111 terminates. Then, the retrieval range update part 111 sets a retrieval end position when update is terminated immediately before to be a retrieval end position at next update start time, and starts the update of the retrieval range by the binary search for the next retrieval word.