To extend the service life of electrical component, including an electric motor with a simple structure, by cooling electrical components provided on a construction machine with hydraulic oil that operates a hydraulic actuator.

Excavating attachment of a construction machine includes a boom cylinder 18, an arm cylinder 20 and a bucket cylinder 22. A unit A1 comprising an electric motor 15 and a hydraulic pump 16 for the boom, a unit A2 comprising an electric motor 23 and a hydraulic pump 24 for the arm, and a unit A3 comprising an electric motor 25 and a hydraulic pump 26 for the bucket are structured each as an integrated actuator. Then, an oil cooler 35 is connected to the return pipe L from each unit A1, A2, A3. Oil cooled by this oil cooler 35 is designed to return to an oil tank 30 after passing a battery 12, a generator 11 and each of electric motors 15, 23, 25.