HYBRID CONSTRUCTION MACHINE

Provided is a hybrid construction machine which can improve temperature control efficiency of an electrical storage device. It includes an engine 1, an assisting electricity generation motor 2 which performs assistance of power for the engine 1 and electricity generation and an electrical storage device 8 which performs transfer of electric power with this assisting electricity generation motor 2. The electrical storage device 8 includes a plurality of battery cells 200, a housing 220 which covers the plurality of battery cells 200 in a state of leaving them separated, a cooling plate 203 which is attached to this housing 220 and performs heat exchange with the plurality of battery cells 200, and a projection 214 which is interposed between the housing 220 and the cooling plate 203 and hinders heat transfer between the housing 220 and the cooling plate 203.