To provide a projection type display device by which a user can simultaneously edit by displaying the same screen of a common electronic document.

The projection type display device is provided with: a display means (1) for forming a written image in an overlapped manner; an image pickup means (3) for photographing the written image formed on the display means (1); a projection means (2) for projecting the image data on the display means (1); an information processing means (4) for adjusting a projection position and a size of the written image photographed by the image pickup means (3) and for pasting it on the electronic document to be displayed on the display means (1); a means for transmitting the photographed image obtained from the image pickup means (3) to an external projection type display device connected via a network; and a means for displaying the photographed image received from the external projection type display device as the photographed image with prescribed transparency to the display image to be displayed on the display means (1) in an overlapped manner.