A motion-based input device includes an inertial sensor acquiring an inertial signal corresponding to a user's motion, a buffer unit buffering the inertial signal at predetermined intervals, a mode classifying unit extracting a feature from the buffered inertial signal and classifying an input mode as either of a continuous state input mode and a symbol input mode based on the extracted feature, and an input processing unit which processes the inertial signal according to the classified input mode to recognize either of a continuous state and a symbol and outputs an input control signal indicating either of the recognized continuous state and symbol. The inertial sensor includes at least one sensor among an acceleration sensor and an angular velocity sensor. The motion-based input device further includes an input button that functions as a switch allowing the user to input a motion.