A position detection system includes: a scan beam illumination section which causes a first-direction line-shaped scan beam that is parallel to the X-axis to scan in the Y-axis direction at a predetermined scanning speed, then causes a second-direction line-shaped scan beam that is parallel to the Y-axis to scan in the X-axis direction at a predetermined scanning speed; a light-receiving section which detects the timings at which the first and second-direction line-shaped scan beams pass through a pointing position on a screen; and a position calculation section which calculates the pointing position by a pointing device on the screen, based on the time from the start of scanning of the first-direction line-shaped scan beam until the passage thereof through the pointing position is detected and the time from the start of scanning of the second-direction line-shaped scan beam until the passage thereof through the pointing position is detected.