Abstract: An index creating apparatus creates indexes of documents displayed on a display unit. The index creating apparatus includes an analyzing unit for analyzing a format of an index word from an input document and for explaining the index word. A display controller registers a specified portion of a document which is displayed on the display unit as the index word, cancels the specified portion of the document which is displayed on the display unit and registered as the index word and retrieves a specified index word from registered index words. The display controller displays the input document and displays the portion corresponding to the index word on the display unit differently from other portions of the input document. A storage stores information related to the registered index words, and a filling unit obtains an output document by filling the index word into the input document with a predetermined format and outputting the output document.