An index database creating apparatus includes a feature extracting unit for extracting features from a content; an index creating unit for creating feature indices of the extracted features; an index selector for selecting one or more of the feature indices based on frequency-based importance levels thereof; and a feature index database for storing therein the selected feature indices along with locations thereof in the content. The index selector obtains the frequency-based importance levels based on frequency distributions of the feature indices in the content and in other contents to be stored in the feature index database.