Hybrid construction machine

A hybrid construction machine includes an engine (8), a generator motor (14), and a hydraulic pump (9). They constitute a power unit (U2), and are connected in series, with the generator motor (14) being disposed between the engine (8) and the hydraulic pump (9) and with a center of gravity of the entire power unit (U2) being positioned closer to the generator motor (14) than the center of gravity of the engine (8). A mount installation bracket (19) is mounted at a side of each flange (15,16) disposed at a corresponding side of the generator motor (14). A generator- motor-side mount device (18) is mounted to the bracket (19).