PURPOSE: To easily designate the input of three-dimensional coordinates by providing a means to detect the horizontal moving amount of a first arm member and a means to detect the respective vertical moving amounts of first and second arm members, and designating the input of three-dimensional coordinates corresponding to the moving position of an operation grip.

CONSTITUTION: An operation grip 15 is supported by first and second arms 12 and 13 freely turnable vertically and further, the first arm is set freely turnable horizontally to a pedestal 11. Therefore, the operation grip 15 can be freely moved in a three-dimensional space according to the operation of an operator. The horizontal displacing amount of the operation grip 15 is detected by a sensor S3, and the vertical displacing amount of the operation grip 15 is detected by sensors S1 and S2. Accordingly, the displacing amount of the operation grip 15 in the three-dimensional space can be calculated based on pulse signals from the sensors S1-S3. Thus, the input of three-dimensional coordinates can be designated without using the plane on a desk.