The invention provides two kinds of structures for a thin-film solar cell that is improved in the adhesive strength and reflectance of a back surface electrode layer. According to the first structure, in a thin-film solar cell in which a transparent electrode layer, a thin-film semiconductor layer, and a back surface electrode layer are laid in stated order on an insulative transparent substrate, the back surface electrode layer consists of a first transparent conductive metal compound layer having a smaller refractive index than a semiconductor that constitutes the thin-film semiconductor layer, a second transparent conductive metal compound layer, and a metal layer. The second transparent conductive metal compound layer contains at least one of components of the first transparent conductive metal compound layer and a component of the metal layer. According to the second structure, in a thin-film solar cell in which a transparent electrode layer, a thin-film semiconductor layer, and a back surface electrode layer are laid in order on an insulative transparent substrate, the back surface electrode layer is a layered body consisting of a silver thin film, and an intermediate thin layer containing silver, oxygen, and a metal element constituting a transparent conductive metal oxide.