An object of the present invention is to provide a method for producing ethanol from polysaccharide alginate contained in a large amounts in brown algae, using the alginate assimilation capacity of the Sphingomonas sp. strain A1 and the strong ethanol production capacity of bacteria such as Zymomonas mobilis. Specifically, a method for producing ethanol using alginate as a raw material comprises causing genes encoding proteins and enzymes involved in Sphingomonas sp. strain A1-derived alginate assimilation and genes encoding enzymes involved in ethanol production to co-exist in a single microorganism and then culturing the microorganism in a medium containing alginate.