A light-driven rotor applied to a water surface includes a bottom plate, a thermally conductive sheet having a base portion covering on an upper surface of the bottom plate and a plurality of leads extended from the border of the base portion and bent downwardly from the edge of the bottom plate to contact the water surface, and a light-absorbing material attached to an upper surface of the thermally conductive sheet for absorbing the light irradiated thereon by a light source and providing light energy required for heating the thermally conductive sheet so that the heat generated by the thermally conductive sheet is conducted to the water surface via the leads to form a gradient change in surface tension, providing a resultant torque for driving the light-driven rotor to rotate. The materials selected for the three-layer structure design of the light-driven rotor are generally applicable, inexpensive and easy to obtain.