PURPOSE: To automatically set the brightness of a liquid crystal display according to the brightness in the place wherein an operator is present wherever operation is started.

CONSTITUTION: The liquid crystal display part 1 is provided with a liquid crystal part 8 on the front and further provided with a contrast variable resistor 2 for manually varying the contrast of the liquid crystal part 8, a brightness variable resistor 3 for automatically and manually adjusting the brightness of the liquid crystal display 1, a photosensor part 4 which measures external brightness, a back light part 9 which emits light to illuminates the liquid crystal part 8 from behind, and a top cover 7 and a reverse cover 10, and a computer main body 5 is provided with a brightness control part 11 which calculates specific brightness from illuminance data sent from the photosensor part 4. Consequently, the photosensor part 4 sends the quantitative illuminance data on the external brightness to a brightness control part 11, which makes the back light part 9 emits light so as to obtain the best liquid crystal display brightness for the user.