An alcohol production system that produces alcohol by alcoholic fermentation using a saccharide solution, including an alcoholic fermentation vessel in which the saccharide solution is fermented by adding yeast to produce alcohol, which is an organic feedstock, and a biomass-hydrothermally-treated-product adding means that adds a biomass hydrothermally-treated product obtained by hydrothermally treating a biomass feedstock to the alcoholic fermentation vessel. The alcohol production system can improve alcoholic fermentation efficiency and realize cost reduction without adding only a mineral salt from outside.