PURPOSE: To increase the operation speed of an object of operation and accurately operates it in an operation direction even when the joy stick is operated to an intermediate area between an X axis and a Y axis.

CONSTITUTION: This device has the joy stick 11 which can be operated in a two-dimensional area and outputs an operation controlled variable by a function; and an operation controlled variable arithmetic circuit 16 calculates the vectors at a position where the joy stick 11 is operated from manipulated variables of the X axis and Y axis, finds the operation controlled variable of the function corresponding to the vector absolute values as a controlled variable for conversion, and recalculates the operation controlled variables of the X axis and Y axis by the controlled variable for conversion and vector directions. Consequently, an operation controlled variable based upon the function is obtained in consideration of the actual manipulated variable and direction of the joy stick operated to the intermediate area and operation similar to operation in the X-axial and Y-axial directions is actualized.