A hydraulic driving device (5, 5a, 5b) for a working machine comprising: a hydraulic pump; a hydraulic actuator driven by pressure oil supplied from the hydraulic pump; a tank that accumulates return oil from the hydraulic actuator; a flow rate control valve that controls a flow of the pressure oil discharged from the hydraulic actuator; and an accumulator that accumulates the pressure oil discharged from a bottom chamber of the hydraulic actuator and flowing to the tank via the flow rate control valve; characterized in that the hydraulic driving device (5,5a,5b) includes: a first differential pressure control valve (201, 211, 221) located between the hydraulic actuator and the accumulator, the first differential pressure control valve (201, 211, 221) performing control on the pressure oil discharged from the hydraulic actuator such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve becomes a predetermined target differential pressure; and a second differential pressure control valve (202, 212, 222) located between the accumulator and the tank 20), the second differential pressure control valve (202, 212, 222) performing control on the pressure oil discharged from the hydraulic actuator such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve and the first differential pressure control valve (201, 211, 221) becomes the predetermined target differential pressure, and the respective first differential pressure control valve 201, 211, 221) and second differential pressure control valve (202, 212, 222) are configured such that the predetermined target differential pressure increases according to an increase in pressure of the pressure oil discharged from the hydraulic actuator. a hydraulic pump; a hydraulic actuator driven by pressure oil supplied from the hydraulic pump; a tank that accumulates return oil from the hydraulic actuator; a flow rate control valve that controls a flow of the pressure oil discharged from the hydraulic actuator; and an accumulator that accumulates the pressure oil discharged from a bottom chamber of the hydraulic actuator and flowing to the tank via the flow rate control valve; characterized in that the hydraulic driving device (5,5a,5b) includes: a first differential pressure control valve (201, 211, 221) located between the hydraulic actuator and the accumulator, the first differential pressure control valve (201, 211, 221) performing control on the pressure oil discharged from the hydraulic actuator such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve becomes a predetermined target differential pressure; and a second differential pressure control valve (202, 212, 222) located between the accumulator and the tank 20), the second differential pressure control valve (202, 212, 222) performing control on the pressure oil discharged from the hydraulic actuator such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve and the first differential pressure control valve (201, 211, 221) becomes the predetermined target differential pressure, and the respective first differential pressure control valve 201, 211, 221) and second differential pressure control valve (202, 212, 222) are configured such that the predetermined target differential pressure increases according to an increase in pressure of the pressure oil discharged from the hydraulic actuator.