To provide a method of detecting the position of image instructing means which is capable of realizing position detection of high accuracy at a low cost.

In this method of detecting the position of the image instructing means, an image control section 3 projects the image for position detection only in the prescribed period during the projection of the display image to a screen 13 and the light which is the projected light of the image for position detection and is reflected to a reflecting pen 14a as the image instructing means is detected by a coordinate detecting section 5, by which the position of the reflecting pen 14a is detected.