PURPOSE: To shorten the time necessary for display by discriminating and reading desired document information with a single scan by a reading head during retrieval on the basis of discrimination information written in a document partition area.

CONSTITUTION: The reading head moves over a magnetic disk surface from the outer circumference to the center to read specified pieces of document information successively while a document partition discriminator 55 selects them. The read pieces of document information are written successively in previously allotted partitions of a coding memory 56 on the basis of the discrimination information under the control of the 1st memory writing part 58 and a single scan on the entire magnetic disk surface is made to read and write all coded pieces 51W54 of document information in the coding memory 56. Then, the coded pieces 51W54 of document information are read out successively and decoded by a decoder 41 to be written in four partitions of a page memory 42 respectively.