PURPOSE: To improve operability of a mouse by adding a button switch to the mouse to hold the maximum shift value of the mouse while said switch is kept pushed and therefore limiting the mouse operating space.

CONSTITUTION: When a button switch of a mouse 10 is kept OFF, the data on the mouse 10 are fetched by a data holding device 2 every fixed time via a reception buffer 1 and a selector 3 and then sent to a system device 11 via a transmission buffer 9. While the selector 3 is changed over by a signal 5 when the button switch is kept ON. Then the data on the mouse 10 is compared with the data held by the device 2 by a comparator 4. Thus the data having the larger absolute value is held by the device 2 and sent to the device 11 via the buffer 9. As a result, the maximum shift value of the mouse 10 is held as long as the mouse 10 is operated with the button switch kept pushed. Thus the operability of the mouse 10 is improved.