To efficiently transmit energy of a battery for a long time, by arranging the battery at the rear part of the upper slewing body and arranging an electric motor at the front part of the battery and connecting a hydraulic pump to the motor and arranging a hydraulic oil tank at the nearby position of the hydraulic pump and arranging a changeover valve for an actuator at the nearby position of the hydraulic pump.

A hydraulic actuator is driven by the power of an electric motor driven by the electric power from a battery 9 mounted on the upper slewing body 6. The electric motor is disposed at the nearby position of the battery 9 and thereby the electric power loss resulting from the resistance of electric cables is reduced. And a hydraulic oil tank is disposed at the nearby position of the hydraulic pump to shorten the hydraulic pipes connecting the hydraulic pump and the hydraulic oil tank, and the hydraulic oil pump and the changeover valve for the actuator respectively and reduce energy loss resulting from the pipe resistance and economize the energy of the battery 9. Accordingly, the battery energy can be efficiently transmitted for a long time.