Disclosed is a waste heat recovery apparatus which comprises: a gas-liquid separator; an expander into which a gaseous working medium separated by the gas-liquid separator flows; a driven machine; a condenser; a first pump; a first heater; a circulation flow passage for serially connecting the gas-liquid separator, the expander, the condenser, the first pump and the first heater in this order; a heat recovery flow passage for allowing a liquid working medium discharged from the gas-liquid separator to merge with the working medium flowing in a portion between the first heater and the gas-liquid separator in the circulation flow passage; and a second pump.