PURPOSE: To correctly obtain movements in the X-direction and the Y-direction of a pen moving plane even if a pen is moved as being held at any part of a pen case by correcting the movement on the pen moving plane by a pen axis vertical direction detecting mechanism and a hand gripping angle storage memory.

CONSTITUTION: An angle formed by a reference plane 21 in a pen axis direction and a plane passing through a pen center axis 22 and perpendicular to the pen moving plane 20 is detected by the pen axis, vertical direction detecting mechanism 2. Besides, the angle which the projection on the pen moving plane 20 of the pen center axis 22 at the time when a pen type mouse is moved on the pen moving plane 20 as being gripped by a hand forms with the Y-direction of the pen moving plane 20 is measured and stored beforehand in a memory 3. Then, the movement detected by a pen movement detecting mechanism 1, the angle detected by the pen axis vertical direction detecting mechanism 2, and the angle stored in the memory 3 are inputted to a correcting means 4, and are calculated, and a corrected coordinate value is inputted to a computer. Thus, the movements in the X-direction and the Y-direction of the pen moving plane can be correctly inputted.