CONSTRUCTION MACHINE

Provided is a construction machine capable of effectively lowering a voltage between terminals of an energy storage unit for use in drive assistance and regeneration without involving an intolerable increase in cost and facility space. The construction machine includes: a work device operable on drive and regeneration sides; an operation device (16) which receives a manipulation and outputs an operation command concerning the work device; a hydraulic unit including a hydraulic motor (7) as a drive source to drive the work device; an electric unit including an electric motor (11) as a drive source and an energy storage unit (23) functioning as a power source for the electric motor (11) to assist driving of the work device by the hydraulic unit; a control device (24, 25) which makes the electric power of the energy storage unit assist the hydraulic unit when the operation device (16) is manipulated for the drive side, and makes the electric motor (11) generate regenerative electric power for supplying the regenerative electric power to the energy storage unit (23) as charging electric power when the operation device (16) is manipulated for the regeneration side; and a power-discharge command unit (26) which commands a discharge of the energy storage unit (23). In the case where the discharge command is issued, the control device (24, 25) operates the electric motor (11) to lower a voltage between terminals of the energy storage unit (23) when the operation device is manipulated for the drive side, and makes only the hydraulic unit decelerate or stop the work device when the operation device is manipulated for the regeneration side.