PURPOSE: To make it possible to refer to document information by visually putting a recognition mark such as a bookmarker to the document information similarly to the reading of a general book.

CONSTITUTION: At the time of receiving an add command ADD for adding a recognition mark to a required information position in document information 21 displayed on a display device 70 from a command means 10, a recognition mark adding means 30 stores the information position corresponding to the added recognition mark in a storage means 20 as recognition mark information 22. At the time of receiving a select command SEL for selecting a required recognition mark out of plural recognition marks displayed on the device 70 from the means 10, a recognition mark retrieving means 50 retrieves an information position corresponding to the selected recognition mark from the information 22. A display control means 60 receiving the commands ADD, SEL simultaneously displays the corresponding document information 21 and recognition mark on the same screen of the device 70.