An inclination of a first unit is detected based on an output from a first acceleration sensor provided in a first unit of a controller, and an inclination of a second unit is detected based on an output from a second acceleration sensor provided in a second unit separate from the first unit. A difference between the inclinations of the first unit and the second unit is detected, and game control is performed using the detected difference. Thus, with a game apparatus using a plurality of acceleration sensors or a plurality of sensors capable of detecting a motion or a posture, a dynamic play is made possible with a high degree of freedom of motion and an intuitive motion input is realized.