In order to form a high-quality Si-based film at high speed, for example, a deposited film forming device according to one aspect of the present invention includes: a chamber; a first electrode arranged in the chamber; and a second electrode arranged in the chamber and spaced a certain distance from the first electrode. The second electrode includes first and second supplying parts. The first supplying part supplies a first material gas and generates hollow cathode discharge. The second supplying part supplies a second material gas higher in decomposition rate than the first material gas.