A heat energy recovery device 1, which recovers heat energy of a heat medium by utilizing a Rankine cycle of a working medium, comprises a first heater 2, a second heater 3, an expander 4, an oil separation unit 12, a condenser 6, a working medium pump 7, and an oil-leading passage 10. When the height of a liquid level in the oil separation unit 12 is less than a lower limit value, a control unit 16 first performs a speed reduction control of the working medium pump 7 to reduce an inflow rate of a working medium into the second heater 3, and after a fixed period of time, performs an opening control for opening an on-off unit 11. By the opening of the on-off valve 11, oil L1 in the second heater 3 is led out to the oil separation unit 12 through the oil-leading passage 10.