To uniformly form a silicon thin film for a solar cell, having an i layer formed with crystalline silicon, on a substrate of a large area to provide a high power solar cell, in a manufacturing method of a silicon thin film solar cell, a silicon thin film, having a structure such that an i layer is sandwiched between a p layer and an n layer, is formed on a substrate with a high frequency plasma CVD method, wherein i layer is formed with crystalline silicon using plasma with pulse-modulated high frequency power, one cycle of pulse modulation includes an ON state for outputting high frequency power and an OFF state for not outputting, an output waveform is modulated to be rectangular, a time of the ON state is 1-100 microseconds, and a time of the OFF state is 5 microseconds or longer.