PURPOSE: To output the signals in accordance with the revolving distance and the revolving direction of a rotary ball by varying the revolving distance in response to the set variable magnification.

CONSTITUTION: A mouse main body 14 contains a roller 7 on its bottom surface and a magnification setting button 6 on its side face as a setting means. When the roller 7 revolves with the movement of the main body 14, the X and Y direction shift extent detection circuits 1 and 2 detects the shift extents of the body 14 in each direction and send the mouse shift extent detection signals 8 and 9 to the X and Y direction distance signal output circuits 3 and 4 respectively. Thus the shift extents are converted into the magnifications and the mouse shift signals 12 and 13 are outputted to a computer. Thus the fine choices are surely selected just by setting the magnification of the shift distant at half when a cursor is moved to the fractionized choices.