PURPOSE: To remarkably improve the operatability of a slave device side working part, by mounting a magnification setting means for setting and changing the magnification of a working amount of the working part to an operation amount of an operating tool.

CONSTITUTION: A controller 16 automatically operates a slave device side working part in a direction corresponding to an operating direction of a corresponding master device side operating tool, by the amount in proportion to the operation amount thereof. When the working with high accuracy, of the working part is needed, the instruction for reducing the magnification of the working amount is given to a magnification setting means 16C mounted on the controller 16 by the operation of the operating means 18a, 18b. The magnification setting means 16C changes the setting of the magnification of the working amount to the operation mount, to be a lower one on the basis of the instruction, so that the slave device side working part can be worked with high accuracy. On the other hand, when the accuracy in working is needed not so much, high magnification is set by the magnification setting means 16C. Whereby the ordinary operation of the operating tool can be easily performed with small power.