A Rankine cycle system includes a boiler configured to apply waste heat to refrigerant circulating in an internal-combustion engine to vaporize the refrigerant; a gas-liquid separator configured to separate gas-liquid two-phase refrigerant, sent from the boiler, into gas phase fluid and liquid phase fluid; a superheater configured to superheat the gas phase fluid, sent from the gas-liquid separator, through heat exchange with exhaust gas of the internal-combustion engine; an expander configured to expand the gas phase fluid, passing through the superheater, to recover thermal energy, and a condenser configured to condense the gas phase fluid, passing through the expander, to return the gas phase fluid to liquid phase fluid. The gas-liquid separator is connected to the internal combustion engine via a refrigerant pipe. The internal combustion engine is fixed onto an engine mount of a vehicle. The gas-liquid separator is fixed to the internal combustion engine via a bracket.