Provided is a hybrid construction machine such that an electric motor is used to drive a swing body, and that even if, for some reason, there arises a situation where the torque of the motor cannot be generated, satisfactory work can be carried out. For the purpose of driving the swing body, the hybrid construction machine is equipped with both a hydraulic motor (27) and an electric motor (25). The hybrid construction machine is also equipped with a controller (80) which switches between a combined swing mode involving the hydraulic motor and the electric motor, and an independent swing mode involving the hydraulic motor. In this respect, sufficient operability and performance can be achieved in both modes. Normally, energy saving operation is performed in the combined swing mode involving the hydraulic motor and the electric motor. If the amount of electric charge stored falls outside a predetermined range, or if an electric abnormality such as an inverter failure occurs, a switch is made to the independent swing mode involving the hydraulic motor, with the result that the swing body can be driven independently by the hydraulic motor.