A method of manufacturing a solar cell, the method includes forming a protective film over a semiconductor substrate, the semiconductor substrate including a base area of a first conductive type and formed of crystalline silicon, wherein the forming of the protective film includes a heat treatment process performed at a heat treatment temperature of approximately 600 degrees Celsius or more under a gas atmosphere including nitrogen, and wherein the heat treatment process includes: a main section, during which the heat treatment temperature is maintained, a temperature increase section before the main section, during which an increase in temperature occurs from an introduction temperature to the heat treatment temperature, and a temperature reduction section after the main section, during which a decrease in temperature occurs from the heat treatment temperature to a discharge temperature.