PURPOSE: To suppress the partial erasing of a text or the display of an excess space by detecting a reduction/enlargement ratio in the reduction/enlargement of a window and reducing/enlarging a text by the same reduction/enlargement ratio as the detected one.

CONSTITUTION: When a command for indicating the reduction/enlargement of the window 1-3 is inputted from a command input device 1-6, a window reducing/enlarging device 1-7 reduces/enlarges the window 1-3 formed by an window forming/registering device 1-10 based upon the command. A reduction/ enlargement ratio detector 1-8 detects the reduction/enlargement ratio based upon the reduction/enlargement of the window 1-3 by the device 1-7 and outputs the detected value to a text reducing/enlarging device 1-9. The device 1-9 reduces/enlarges the test 1-4 accessed by a text access device 1-11 and displayed on a screen 1-2 based upon the reduction/enlargement ratio inputted from the detector 1-8.