To effectively and efficiently utilize electronized information and to improve the operability and convenience of a user by generating an abstract of a common document having large relativity with relative words and displaying the relative words and abstract on a screen so that they correspond to each other.
A ranking engine 204 inputs a relative word list 203 of the common document 300 from a natural language process module 200, weights the respective relative words, decide the importance of each sentence, and ranks the respective sentences to generate a ranking list 205. A ranking engine 204 generates ranking lists 205 by common documents. Then an abstract generation module 209 selects a previously set number of sentences from the top ranking and generates an abstract by using the selected sentences. Further, a display control module 210 inputs the abstract and display it on the screen of a display while making it correspond to the relative words of the corresponding specific document 201.