An information input/output device having an intuitive operating feeling and improved information viewing and discriminating properties. The device comprises an superposing image extraction unit 101 extracting a portion for superpositional display from an image to output the extracted image portion as an superposing image, a mask pattern generating unit 102 generating a mask pattern, effectors 113, 114 processing the superposing image, and the mask pattern based on the effect designation information, and a base image generating unit 115 synthesizing the mask pattern image and the original image to generate a base image. The device also comprises a switcher 116, brightness/contrast controllers 117, 118 adjusting the brightness or contrast of the display image switching means 112, a control unit 111, superpositional image display unit 124 for superposed demonstration of display image planes of the displays 122, 123 and a display position adjustment mechanism 121. The display information of the image for display in superposition is demonstrated at a position which appears to be floated or recessed from the basic display plane.