A hydraulic drive apparatus provided for a construction machine including an upper slewing body capable of slewing, the hydraulic drive apparatus comprising: a plurality of hydraulic actuators (7, 33) including a slewing motor that slews the upper slewing body; a hydraulic pump (31, 32) configured to discharge hydraulic fluid for moving the hydraulic actuators (7, 33); a regenerative motor driven by a part of the hydraulic fluid discharged from the hydraulic actuators (7, 33) to perform regenerative action; a hydraulic brake circuit including a relief valve (38, 39) and configured to perform anti-cavitation action for returning the hydraulic fluid on a meter-out side of the slewing motor to a meter-in side during deceleration of slewing of the upper slewing body to prevent cavitation from occurrence and to perform hydraulic brake action by the relief valve (38, 39); a makeup line connecting the hydraulic brake circuit to a tank; characterized by a back pressure valve provided in the makeup line and configured to generate back pressure in the makeup line; a first regeneration tank line for returning regeneration discharge fluid, which is hydraulic fluid discharged from the regenerative motor, to the tank in a route in which the regeneration discharge fluid passes through the back pressure valve; a second regeneration tank line for returning the regeneration discharge fluid directly to the tank in a route in which the regeneration discharge fluid bypasses the back pressure valve; a regeneration-tank-line selector valve having a first position for allowing the regeneration discharge fluid to return to the tank through the first regeneration tank line and a second position for allowing the regeneration discharge fluid to return to the tank through the second regeneration tank line, the regeneration-tank-line selector valve being selectable between the first and second positions; a slewing deceleration detection section (51, 64) configured to detect that the slewing motor is in a deceleration state; and a regeneration-tank-line-selection control section configured to shift the regeneration-tank-line selector valve to the first position when the slewing deceleration detection section (51, 64) detects the deceleration state and shift the regeneration-tank-line selector valve to the second position when the slewing deceleration detection section (51, 64) does not detect the deceleration state. a plurality of hydraulic actuators (7, 33) including a slewing motor that slews the upper slewing body; a hydraulic pump (31, 32) configured to discharge hydraulic fluid for moving the hydraulic actuators (7, 33); a regenerative motor driven by a part of the hydraulic fluid discharged from the hydraulic actuators (7, 33) to perform regenerative action; a hydraulic brake circuit including a relief valve (38, 39) and configured to perform anti-cavitation action for returning the hydraulic fluid on a meter-out side of the slewing motor to a meter-in side during deceleration of slewing of the upper slewing body to prevent cavitation from occurrence and to perform hydraulic brake action by the relief valve (38, 39); a makeup line connecting the hydraulic brake circuit to a tank; characterized by a back pressure valve provided in the makeup line and configured to generate back pressure in the makeup line; a first regeneration tank line for returning regeneration discharge fluid, which is hydraulic fluid discharged from the regenerative motor, to the tank in a route in which the regeneration discharge fluid passes through the back pressure valve; a second regeneration tank line for returning the regeneration discharge fluid directly to the tank in a route in which the regeneration discharge fluid bypasses the back pressure valve; a regeneration-tank-line selector valve having a first position for allowing the regeneration discharge fluid to return to the tank through the first regeneration tank line and a second position for allowing the regeneration discharge fluid to return to the tank through the second regeneration tank line, the regeneration-tank-line selector valve being selectable between the first and second positions; a slewing deceleration detection section (51, 64) configured to detect that the slewing motor is in a deceleration state; and a regeneration-tank-line-selection control section configured to shift the regeneration-tank-line selector valve to the first position when the slewing deceleration detection section (51, 64) detects the deceleration state and shift the regeneration-tank-line selector valve to the second position when the slewing deceleration detection section (51, 64) does not detect the deceleration state.