A method of manufacturing a solar cell is discussed. The method of manufacturing the solar cell includes: forming a conductive region on a semiconductor substrate; forming an electrode connected to the conductive region; and post-processing the semiconductor substrate to passivate the semiconductor substrate. The post-processing of the semiconductor substrate comprises a main processing process for heat-treating the semiconductor substrate while providing light to the semiconductor substrate. A temperature of the main processing process is about 100° C. to about 800° C., and the temperature and light intensity of the main processing process satisfy Equation of 1750−31.8·T+(0.16)·T2≦I. Here, T is the temperate (° C.) of the main processing process, and I is the light intensity (mW/cm2) of the main processing process.