PURPOSE: To efficiently manufacture hydrogen from an org. substance by decomposing alcohol fermented from the org. substance into gaseous hydrogen and CO2 by the photocatalysis of a semiconductor.

CONSTITUTION: An org. substance contg. starch, cellulose or saccharides such as agricultural or forestry waste is put in an alcohol fermentation tank 1 from an arrow A and converted into alcohol in the presence of a microorganism. A soln. based on the converted alcohol is introduced into a semiconductor catalyst tank 2 through an arrow B. The tank 2 has been filled with fine powder of a semiconductor having photocatalysis. The introduced alcohol soln. is decomposed into gaseous hydrogen and CO2 on the surface of the semiconductor powder in the tank 2 by the action of light 4 with energy above the band gap of the semiconductor irradiated from the outside. This gaseous mixture of hydrogen with CO2 is introduced into a separation tank 3 through an arrow C and separated into hydrogen and CO2 to feed hydrogen.