To provide a CIGS-based thin-film solar battery capable of preventing bad influences of solution caused by the CBD method.

A rear face electrode is formed on one surface of a film substrate (S106), a CIGS semiconductor layer is formed (S114), and a buffer layer is solution-grown by the CBD method (S118). By the CBD method is performed, a protection layer for preventing contact of chemical liquid for the CBD method is preliminarily formed on the other surface of the film substrate (S116). After the formation of the buffer layer, the protection layer is removed (S120), and a connection wiring layer (a second connection wiring layer) is formed on the other surface.