A hybrid construction machine comprising: an engine; a generator-motor configured to make a generator action and a motor action; a hydraulic pump configured to be driven by the engine; a hydraulic actuator configured to be operated by the hydraulic pump as a hydraulic pressure source; an actuator regeneration section configured to make a regenerative action of generating actuator regenerated-electric-power through return fluid from the hydraulic actuator; an electric storage device capable of being charged and discharging electric power stored therein; a charging-rate detector configured to detect a charging rate of the electric storage device; and a control section configured to perform: causing the electric storage device to be charged with electric power generated by the generator-motor through the generator action and the actuator regenerated-electric-power generated by the actuator regeneration section through the regenerative action; causing the generator-motor to make the motor action through electric power stored in the electric storage device 12) to thereby assist the engine; wherein the actuator regeneration section includes: a regeneration circuit connected to the hydraulic actuator to allow return fluid from the hydraulic actuator to be flowed therein; a regeneration motor provided in the regeneration circuit to be rotationally driven by the return fluid from the hydraulic actuator; and a regeneration generator configured to be driven by the regeneration motor to generate regenerated-electric-power, characterized in that the control section is configured to perform a regeneration control of stopping the generator action of the generator-motor and restricting the actuator regenerated-electric-power to be generated by the actuator regeneration section when the charging rate of the electric storage device detected by the charging-rate detector is equal to or greater than a preset charging-rate limitation value (αs), wherein the actuator regeneration section further includes a flow regulating valve configured to regulate a regeneration-flow-rate which is a flow rate of the return fluid flowing in the regeneration circuit, and wherein the control section is configured to perform the regeneration control through the regulation of the regeneration-flow-rate by the flow regulating valve. an engine; a generator-motor configured to make a generator action and a motor action; a hydraulic pump configured to be driven by the engine; a hydraulic actuator configured to be operated by the hydraulic pump as a hydraulic pressure source; an actuator regeneration section configured to make a regenerative action of generating actuator regenerated-electric-power through return fluid from the hydraulic actuator; an electric storage device capable of being charged and discharging electric power stored therein; a charging-rate detector configured to detect a charging rate of the electric storage device; and a control section configured to perform: causing the electric storage device to be charged with electric power generated by the generator-motor through the generator action and the actuator regenerated-electric-power generated by the actuator regeneration section through the regenerative action; causing the generator-motor to make the motor action through electric power stored in the electric storage device 12) to thereby assist the engine; wherein the actuator regeneration section includes: a regeneration circuit connected to the hydraulic actuator to allow return fluid from the hydraulic actuator to be flowed therein; a regeneration motor provided in the regeneration circuit to be rotationally driven by the return fluid from the hydraulic actuator; and a regeneration generator configured to be driven by the regeneration motor to generate regenerated-electric-power, characterized in that the control section is configured to perform a regeneration control of stopping the generator action of the generator-motor and restricting the actuator regenerated-electric-power to be generated by the actuator regeneration section when the charging rate of the electric storage device detected by the charging-rate detector is equal to or greater than a preset charging-rate limitation value (αs), wherein the actuator regeneration section further includes a flow regulating valve configured to regulate a regeneration-flow-rate which is a flow rate of the return fluid flowing in the regeneration circuit, and wherein the control section is configured to perform the regeneration control through the regulation of the regeneration-flow-rate by the flow regulating valve.