A method for film-forming a buffer layer to be used for a solar cell, the buffer layer being disposed between a light absorbing layer and a transparent conductive film. Specifically, in this buffer layer film-forming method, a solution is formed into a mist, the solution containing zinc and almuminum as metal raw materials of the buffer layer. Then, a substrate disposed in the atmosphere is heated. Then, the mist of the solution is sprayed to the substrate being heated.