PURPOSE: To simultaneously point plural coordinate positions by plural pointing devices on a screen which is magnified and projected.

CONSTITUTION: The screen of a display device 6 is magnified and projected on a screen 4 by a projector. When the pointing devices 30 and 32 which generates plural different wavelength signals supplies the beams onto the screen 4, these optical signals are reduced by an optical system and the optical signals of specific wavelengths are supplied to the image sensors 20 and 22. The position signals supplied from both sensors 20 and 22 against plural coordinate positions on the screen 4 are converted into the plotting data and supplied to the device 6. The image formed from the plotting data is magnified and projected on the screen 4. Thus an operator can form an image while pointing the positions by plural pointing devices.