Related keywords having certain relations to a target keyword are extracted from a unit storing keywords according to relations among each other. Expressions corresponding to the target keyword and related keywords are read from a unit storing expressions correspondingly with each stored keyword, each expression having been extracted from a content containing the corresponding keyword. A commonness between the expressions corresponding to each related keyword and the target keyword is calculated. An association between each related keyword and the target keyword is calculated using a distance for each related keyword from the target keyword and the commonness. A related keyword having a certain association is extracted as a same-region keyword in a same region as the target keyword. A drawing including the target keyword and related keywords arranged according to the associations is output with the same-region keyword displayed distinguishably from other related keywords not included in the same region.