Abstract: In an idea processor, a plurality of sentences are managed in a hierarchical structure having a plurality of levels. Eight or less sentences are developed from a key sentence, and these nine or less sentences are displayed in a nested structure on a screen such that the key sentence is displayed at the center cell of nine cells arranged in a 3.times.3 matrix, while the developed sentences are displayed in cells that surround the center cell. Since the number of sentences that are developed from the key sentence is limited to eight, the idea processor is easier for a beginner to use, as compared to a conventional idea processor in which the number of sentences that are developed from a key sentence is not limited. Moreover, the nested displayed 3.times.3 cell structure makes it easier to grasp the entire structure of the sentences on a screen.