PURPOSE: To obtain a compact and light character input device by providing a sphere which can be rotated in any direction and to which a magnetic pole is magnetized and detection parts detecting the direction of rotation and the rotational amount.

CONSTITUTION: The input device 1 is constituted of a pen-like whole shape and a ball 2 is rotatably fitted to the tip part in any direction in such a way that a part of an external peripheral surface can touch an external part like the pen tip of a ball pen. The ball 2 is a magnetic thin film ball where an S-pole and an N-pole are alternately magnetized on the surface. An X-direction detector and a Y-direction detector 4 detecting the rotational direction and the rotational amount of the ball 2 are provided in the input device 1 adjacently to the surface of the ball 2. The rotational direction and the rotational amount detected in the detectors 3 and 4 are converted into character patterns and are radio-transmitted to a mainbody by a transmitter 6. Thus, the compact and light input device for a character can be obtained without the need of a key for detecting the character only by executing a simple operation such as to write the character to be inputted.