The game apparatus obtains angular velocity data and acceleration data from an input device equipped with at least an angular velocity sensor and an acceleration sensor, and determines whether or not a ball has been thrown in accordance with the angular velocity data. When it is determined that ball-throwing is fulfilled, the game apparatus calculates the intensity of swinging the input device and a curve amount. The game apparatus applies a force and a curve to a ball in accordance with the calculated intensity of swinging and the curve amount, and performs a process of causing the ball to move and curve in a predetermined direction.