Information output system, information output device and display device

The objective of the present invention is, when an information display device is outputting image information from the information output device to a display device that is desired for display upon the display device, to simultaneously display the display image that is specific to the information output device, without switching input, during display of an image which has been input from another input path for which the information output device is not an output source. The information output system comprises a display device (10), and an information output device (20) which outputs information to cause the display device (10) to display an image thereupon, which are connected. The display device (10) switches the input path of the video image in order to display the input video image for the display device (10) upon the display screen. Then, during display of the video image that is input from the input path for which the information output device (20) is not an output source, a display image is generated on the basis of the information for displaying the image that has been output from the information output device (20), and the same is superimposed and displayed upon the video image for which the information output device is not an output source.