A work machine comprising: - a hydraulic pump; - a hydraulic actuator for driving the work machine; - an operating device for operating the hydraulic actuator; and - a regenerating device for recovering a return fluid flowing back from the hydraulic actuator; - a fluid line for allowing the return fluid from the hydraulic actuator to flow through the line; - a section (32a1) for branching the fluid line into a plurality of fluid lines (33, 34); - a recovery line serving as one of the branch fluid lines (33, 34), the recovery line including the regenerating device; - a discharge line serving as the other of the branch fluid lines (33, 34), the discharge line being for discharging the return fluid to a tank; - a flow control device disposed in the discharge line, the flow control device being adapted to control a flow rate of the return fluid; - an operation amount detector for detecting the operation amount on the operating device; - a discharge flow rate computing unit for acquiring a detection signal from the operation amount detector and calculating a target discharge flow rate of the return fluid flowing through the discharge line; - a regeneration flow rate computing unit for acquiring the detection signal from the operation amount detector and calculating a target regeneration flow rate of the return fluid flowing through the recovery line; and - a control device for controlling the flow control device according to the target discharge flow rate and also controlling the regenerating device according to the target regeneration flow rate, characterized in that the discharge flow rate computing unit is configured to calculate, between a time at which a lever manipulation of the operating device is started and a time at which the hydraulic fluid starts flowing to the regenerating device side, a target discharge flow rate that is equal to a target discharge flow rate as a target flow rate of a return fluid flowing out from the actuator to the tank with respect to a lever manipulation signal from the operating device, and calculate, after the time at which the hydraulic fluid starts flowing to the regenerating side, the target discharge flow rate by adding a lag signal to the target discharge flow rate; and the regeneration flow rate computing unit is configured to calculate, between the time and the time, a target regeneration flow rate as zero, and calculate, after the time, the target regeneration flow rate by adding the lag signal to the target regeneration flow rate which is obtained by subtracting the target discharge flow rate from a target flow rate of the return fluid flowing out from the actuator with respect to the lever manipulation signal from the operating device. - a hydraulic pump; - a hydraulic actuator for driving the work machine; - an operating device for operating the hydraulic actuator; and - a regenerating device for recovering a return fluid flowing back from the hydraulic actuator; - a fluid line for allowing the return fluid from the hydraulic actuator to flow through the line; - a section (32a1) for branching the fluid line into a plurality of fluid lines (33, 34); - a recovery line serving as one of the branch fluid lines (33, 34), the recovery line including the regenerating device; - a discharge line serving as the other of the branch fluid lines (33, 34), the discharge line being for discharging the return fluid to a tank; - a flow control device disposed in the discharge line, the flow control device being adapted to control a flow rate of the return fluid; - an operation amount detector for detecting the operation amount on the operating device; - a discharge flow rate computing unit for acquiring a detection signal from the operation amount detector and calculating a target discharge flow rate of the return fluid flowing through the discharge line; - a regeneration flow rate computing unit for acquiring the detection signal from the operation amount detector and calculating a target regeneration flow rate of the return fluid flowing through the recovery line; and - a control device for controlling the flow control device according to the target discharge flow rate and also controlling the regenerating device according to the target regeneration flow rate,