In this study, four kinds of porous glass beads were synthesized. Hydrogen-producing bacteria were immobilized in the porous glass beads. The effect of the pore size of the porous glass beads on the hydrogen yield was examined by using a batch-type fermenter. The hydrogen-producing bacteria were screened by heat-shock treatment of the anaerobic sludge containing the bacteria in a wastewater treatment plant. The heat-shock treatment was conducted at 343 K for 30 min. When the pore size was 10 mu m or more, the porous glass beads prevented the washout of bacteria from the fermenter. Continuous hydrogen production was realized by using porous glass beads with a pore size of about 20 mu m. The hydrogen yields obtained with porous glass beads were much higher than those obtained without porous glass beads. In the absence of porous glass beads, lactic acid fermentation occurred.