Abstract: A nucleic acid information processing device includes a storage unit that stores first base sequence information including information on a plurality of base sequences, and second base sequence information including information on a plurality of base sequences; a threshold value receiving unit adapted to receive information that identifies a similarity threshold; a hybridization unit adapted to identify a degree of similarity and a starting position and a finishing position of a similar portion for one to one combinations with the base sequences included in the first base sequence information as a target, and the base sequences included in the second base sequence information as a probe; and a similar base sequence counting unit adapted to count for each probe a number of the targets for which the identified degree of similarity is greater than or equal to the similarity threshold, and storing the count in the storage unit.