In order to prevent interception of the information through the leakage electromagnetic waves when transmitting the information using an image display unit, an image converter generates plural converted images, stores the generated converted images in an image storage, an image output unit reads out the converted images from the image storage and transmits the converted images to a screen control unit successively. The screen control unit displays a reception image on an image display unit. The image output unit outputs the converted image group at a high speed, thereby performing a switching display on the image display unit, and to show an image visually equivalent to the input image.