Respective orientations (a pitch angle, a roll angle, and a yaw angle) of the input device are detected based on angular velocity data outputted from a gyro sensor unit of an input device. Then, it is determined whether the pitch angle is within a first range or within a second range. When it has been determined that the pitch angle is within the first range, a posture of an object is updated based on the roll angle. When it has been determined that the pitch angle is within the second range, the posture of the object is updated based on the yaw angle. Accordingly, operability can be improved in a game executed in accordance with an orientation of the input device.