A shooting game is provided based on videos reproduced on a computer by using an augmented reality technology. A 3D graphic object is matched with an existing video by rendering the 3D graphic object and a segmentation object mask of the existing video is overlaid on the 3D graphic object. As a result, three-dimensional effect of the game environment is greatly increased. Further, interactions between the computer and a gamer can be processed by using a gun simulator such as a mouse, a key board, a joystick, and the like. Since the game is played based on the video containing actual elements, the reality of the game environment is greatly enhanced compared to conventional cases where only virtual elements created by using computer graphics are utilized. Therefore, it becomes possible to produce a game having more various interesting scenario with a more real-world-like game environment.