Rankine cycle device of internal combustion engine

A Rankine cycle system for an internal combustion engine, comprising a first Rankine cycle (2A) operated by a first working medium and a second Rankine cycle (2B) operated by a second working medium, each of the Rankine cycles (2A and 2B) being comprised of an evaporator (3A, 3B) for heating a liquid-phase working medium by waste heat from the internal combustion engine (1) to generate a vapor, an expander (4) for converting the heat energy of the vapor discharged by said evaporator (3A, 3B) into a mechanical energy, a condenser (5A, 5B) for cooling the vapor discharged by said expander (4) to return the vapor into the liquid-phase working medium, and a supply pump (6A, 6B) for supplying the water discharged by said condenser (5A, 5B) to said evaporator (3A, 3B), wherein

• said evaporator (3A) in said first Rankine cycle (2A) and said evaporator (3B) in said second Rankine cycle (2B) are respectively disposed at locations upstream and downstream of an exhaust emission control device (8) mounted in an exhaust passage (7) for the internal combustion engine (1);
• said first working medium is of a boiling point higher than that of said second working medium;
• and the capacity of said supply pump (6A) in at least said first Rankine cycle (2A) is variable.