In order to establish an efficient inactivation process of aerobic bacteria, yeast, and mold contained in a solution discharged from a soaking germination process in producing germination brown rice, the germs were inactivated in a photocatalytic reactor where a laminated catalyst was prepared by coating and drying emulsion of commercial photocatalyst on a stainless steel plate. A combination process of filtering with the diatomaceous earth produced in Akita Prefecture and photocatalytic reaction was also evaluated for the effective inactivation of the germs. A prototype of laminated photocatalyst with blacklight lamps was effective for inactivation of aerobic bacteria, yeast, and mold contained in a solution discharged from a soaking germination process. Inactivation rates of the germs were affected by distance between blacklight lamp and photocatalyst surface (r(2)) and thickness of solution layer (1); their rates tended to be lower as I became larger than 3X 10(-3) m even under the thin layer zone. By applying suction filter with the diatomaceous aid to sample solution, ca. 90% of aerobic bacteria and 100% of yeast and mold were removed. A combination of diatomaceous filter and photocatalysis proved to be efficient for inactivation of aerobic bacteria. To kinetically formulate the rate of inactivation for germs by a laminated photocatalyst, a single-hit with multitarget model with the light intensity on the photocatalyst surface 1, estimated by the radial light model, was 4 applicable only tinder thin liquid-layer conditions, while introduction of the effective light intensity I(eff) proved to represent observed results well by adopting a single set of target number m and inactivation efficiency eta for the inactivation of aerobic bacteria under various values of r(2), and I irrespective of filtering or unfiltering of sample solution. The value of I(eff)/I became smaller as I got bigger, and it was nearly identical irrespective of filtering or unfiltering of sample solution. The values of I(eff) obtained for the aerobic bacteria also gave good relationship to the observed results for yeast and mold; the values of target number and inactivation efficiency were almost the same as the ones for aerobic bacteria.