In producing a thin film solar battery using a semiconductor film producing apparatus, a semiconductor film is formed on a substrate by glow discharge decomposition. The substrate is transported in a desired direction within a glow discharge space. A substrate heating unit heats the substrate at different temperatures along the desired direction in which the substrate is transported. Consequently, a plurality of semiconductor layers having different hydrogen concentrations are laminated at desired thicknesses with desired characteristics. A glow discharge generating unit generates high frequency power having different frequencies and/or different power outputs along the desired direction in which the substrate is transported.