To enhance operativeness by detecting inclination quantity of a control lever for making the first and the second operations in the X, Y axial directions on a plane, making outputs in such a manner as being capable of carrying out both operations simultaneously, and calculating operational speeds respectively in response to those outputs.

The longitudinal inclination and the lateral inclination of a control lever 26 are defined as contractive operation of boom and turning operation thereof respectively. When the control lever 26 is forced to incline in the intermediate direction between directions of Y shaft and X shaft, output is generated to both X shaft, Y shaft potentiometers 23, 33 to be inputted in a controller 41, and the operational speed responding thereto is outputted to an actuator 28 as an hydraulic pressure information. The relationship between an output value of potentiometer and an oil pressure value is recorded in ROM 42. When the relationship between the output value and the oil pressure value is set in linear relationship, the boom contraction speed decreases linearly and a boom turning speed increases linearly as the control lever 26 is moved from Y shaft direction toward X direction. Accordingly improvement in operativeness can be attempted.