An object of the present invention is to provide a construction machine that can use the return oil from a hydraulic actuator effectively. For this purpose, a controller computes a flow rate of the return oil from a first hydraulic actuator on the basis of an operation signal from a first operation device, computes a flow rate of oil to be supplied to a second hydraulic actuator on the basis of an operation signal from a second operation device, sets smaller one of the flow rate of the return oil and the flow rate of the oil to be supplied, as a regeneration flow rate that is a flow rate of oil to be regenerated in the second hydraulic actuator, sets a flow rate obtained by subtracting the regeneration flow rate from the flow rate of the return oil, as a recovery flow rate that is a flow rate of oil to be recovered to a pressure accumulating device, adjusts an opening degree of a first control valve 2 such that a flow rate of oil supplied from the first hydraulic actuator to the pressure accumulating device coincides with the recovery flow rate, and adjusts an opening degree of a second control valve such that a flow rate of oil supplied from the first hydraulic actuator to the second hydraulic actuator coincides with the regeneration flow rate.