To reduce the energy consumption of a pilot pump.

The pilot pump 43 is provided for supplying pilot pressure oil to a direction change-over valve 41 via pilot valves 54, 55 to change over the direction change-over valve 41. A check valve 45 is provided in a discharge duct 44 between the pilot pump 43 and each of the pilot valves 54, 55. The pilot pump 43 is driven by a special pilot electric motor 42. The pilot electric motor 42 is started when hydraulic pressure between each of the pilot valves 54, 55 and the check valve 45 is smaller than a set value, and it is stopped when it is not smaller than the set value.