A game processing device processes a simulated game wherein an input device is modeled on an instrument required for a prescribed action in real life. This game processing device comprises game developing means for developing a game simulating said real-life action and providing a display indicating that said instrument has received an impact at a timing during said game corresponding to a time when said instrument would receive an impact during said real-life action; and instruction means for outputting an instruction signal to said input device indicating that said impact has been received at a timing during said game corresponding to a time when said impact would be received. When movement information indicating the movement of said input device and supplied by said input device reaches prescribed conditions, the development of the game by said game developing means is changed.