As an example, a value obtained by adding the magnitudes of a plurality of angular velocities around respective axes indicated by angular velocity data obtained from an input device including gyroscopic sensors, is used to calculate a rotation parameter indicating a rotation amount. A predetermined object which is rotated, depending on the rotation amount corresponding to the rotation parameter, is displayed on a display device. As another example, when it is determined, based on the angular velocity data, that the attitude of the input device is stable, a stability flag which indicates that the attitude of the input device has been at least once stable is set and updated to ON. When there is an input device whose stability flag is OFF, the aforementioned determination is performed and a screen including a result of the determination is displayed on a display device.