A waste heat recovery system having a Rankine cycle in which a boiler, an expander, a condenser, and a circulation pump are installed on a circulation path in which working fluid is circulated according to the present disclosure includes: a plurality of boilers configured to be connected to the circulation path of the Rankine cycle through connection pipes between the expander and the circulation pump; and first and second direction control valves configured to be installed at the top and at the bottom of the plurality of boilers to shift flow directions of the working fluid to the plurality of boilers.