Abstract: In a drive system, there is provided a waste heat recovering device forming a Rankine cycle by an evaporator for heating water with waste heat of an internal combustion engine to generate high-pressure vapor, the internal combustion engine being connected to a transmission, a displacement-type expander for converting high-pressure vapor generated by the evaporator to an output with constant torque, a condenser for liquefying low-pressure vapor discharged from the expander, and a feed pump for supplying water liquefied by the condenser to the evaporator. The expander is connected to a power generator/motor via a planetary gear mechanism, and the expander is connected to an output shaft of the internal combustion engine via the planetary gear mechanism and a belt-type continuously variable transmission.