A silicon thin film solar cell is discussed. The silicon thin film solar cell includes a substrate on which light is incident, a first electrode positioned on the substrate at a surface opposite a surface of the substrate on which the solar light is incident, a second electrode positioned on the first electrode, at least one photoelectric conversion unit positioned between the first electrode and the second electrode, and a back reflection layer positioned between the at least one photoelectric conversion unit and the second electrode. The back reflection layer includes a first reflection layer formed of a material having an absorption coefficient equal to or less than 400 cm−1 with respect to light having a wavelength equal to or greater than 700 nm.