<p>There are provided: control valves 22 - 24 that control flow of pressure oil from the hydraulic source 21 to the hydraulic actuators 15 - 17; electric lever devices 51 - 53 that output electrical operation signals v51 - v53 in correspondence to lever operation; electromagnetic proportional valves 25 - 30 through which control pressures for controlling the control valves 22-24 are output; a pressure calculating unit 50 that calculates control pressures P25 - P30 in correspondence to the operation signals V51 - v53; a control unit 50 that controls the electromagnetic proportional valves 25 - 30 so that control pressures to be output from the electromagnetic proportional valves 25 -30 become the control pressures P25 - P30 that have been calculated; a high-pressure selection circuit 41 - 44 that selects a higher pressure between control pressures that have been output from the electromagnetic proportional valves 25 - 30; pressure detectors 45 and 46 that detect a control pressure selected by the high-pressure selection circuit 41 - 44; an abnormality determination unit 50 that determines an abnormality in the electromagnetic proportional valves 25 - 30 based upon the control pressure detected by the pressure detectors 45 and 46 and the control pressure calculated by the pressure calculating unit; and an inhibiting device 47 and 48 that prohibits control of the control valves 22 - 24 when it is determined that an abnormality has occurred in the electromagnetic proportional valves 25 - 30.</p>
