PURPOSE: To display simultaneously the 1st and the 2nd pictures when the display of the 1st and the 2nd pictures is switched and to simplify the constitution of a device, by successively adjusting the luminance of both pictures and stopping both pictures at optional luminance by means of a luminance control switch.

CONSTITUTION: A display section 40, display driving circuit section 30, luminance control section 50, picture memory section 10, picture memory controlling section 20, control section 60, and luminance controlling key 70 are installed to a document display device. The luminance control section 50 consists of a counter section 51, complement generating section 52, and signal selecting section 53 and information of the 1st and 2nd pictures read out from areas 11W13 of the memory section 10 is displayed on the display section 40. When this display is made, luminance indicating information which successively lowers the luminance of the 1st picture and another luminance indicating information which gradually raises the luminance of the 2nd picture are given to the circuit section 30 from the luminance control section 50. The 1st and 2nd pictures are displayed simultaneously on the display section 40 by stopping both the pictures at optional luminance conditions by means of the luminance control key 70. Thus the constitution of the document display device is simplified.