To provide a practical engine waste heat recovery power-generating turbo system for recovering the energy discarded from an engine in the form of electric power.

The engine waste heat recovery power-generating turbo system 1 generates electricity by using the waste heat in the reciprocating engine 3 including a jacket cooling water circulation system 9, and an exhaust passage 15 for exhausting high temperature combustion gas in the form of exhaust gas. The engine waste heat recovery power-generating turbo system includes a medium circuit 27 which uses a low boiling point medium whose critical temperature is about 80-200°C, and forms a closed loop Rankine cycle by an evaporator unit 33, a turbine 35 for expanding the low boiling point medium, a condenser 37, and a turbo pump 39 for boosting the low boiling point medium; and a generator 29 which is coaxially coupled to the turbine 35, and generates electricity by being rotatingly driven by the turbine 35 that rotates as the low boiling point medium expands. The evaporator unit 33 includes an exhaust gas heat exchanger 45 for changing the low boiling point medium into the vapor phase by performing thermal exchange at least between the exhaust gas and the low boiling point medium.