In this paper, we describe AR squash game, which is a squash-style game based on AR (augmented reality) technique. We made this game using AR technique to estimate geometric information of images taken from a CCD camera. A CCD camera takes real-time images of a room formed by some number of walls, and the geometric information of the image is estimated using markers attached on the walls. By the geometric information and motion data of a ball created internally, a realistic scene is generated, in which the ball moves like a real one. And a user watches the computer screen displaying the mixed image, and tosses the ball using a racket connected to motion tracker. The position and the motion data of the racket is received from a 3D motion tracker