PURPOSE: To quickly and easily grasp a document by displaying a key word contained in a document image on a display screen in an emphasized form and with distinction secured from the parts of other words.

CONSTITUTION: A selection part 6 selects a character that is coincident with a registered key word stored in a registered key word memory 7 as a key word out of those characters read out of a document or a character string including plural characters arrayed continuously. A coordinate designation part 8 decides the coordinates showing the position of each selected key word in the document. The coordinate data are stored in a key word memory 9 together with the key word data. An emphasis display part 10 displays the part of each key word on the screen of a CRT display 11 in an emphasized form and with distinction secured from the parts of other words based on each key word stored in the memory 9 and their coordinate data. Thus the document is quickly and easily grasped.