1. A pointed position detection system which detects a position pointed by a pointer within a predetermined image display region, the system comprising: image pick-up means for picking up an image of the image display region; means for storing an image for differential image generation which is generated by picking up an image of the image display region on which a uniform image is displayed; differential image extraction means for extracting a differential image based on the image for differential image generation and a pointing image which is generated by picking up an image of the image display region in which a pointing action is performed; and means for detecting a pointed position in the pointing image comprised within the image display region, based on the extracted differential image.