NOVELTY - A method and apparatus for producing succinic acid, by adding and suspending agricultural and forest industrial waste material such as rice straw, chaff, rice bran, wheat bran and wood scraps in water, saccharifying using acids such as concentrated sulfuric acid, subjecting to heating and pressurization, neutralizing with alkali such as sodium hydroxide and proliferating succinic acid fermenting microorganisms on substrate.    USE - For producing succinic acid and other organic acids such as lactic acid, citric acid, malic acid, acetic acid, formic acid and propionic acid, which are useful as raw material for preparation of biodegradable plastics, pharmaceutical, chemical product and seasoning. The residue or fermented liquor produced by organic acid fermentation is useful in the manufacture of fertilizer, manure, soil improving material, probiotic formulation, health food, SCP, etc (claimed).    ADVANTAGE - The method enables to produce succinic acid economically, by using the agricultural and biowaste material such as rice straw and wood scrap and has high industrial availability.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for :    (1) method of acquiring microorganism strain capable of carrying out succinic fermentation of biowaste material, involves cultivating sample liquid such as fermented food, soil or compost in a culture medium comprising neutralized biowaste material as the sole source of saccharide, pH indicator such as BCP, reinoculating and cultivating the isolate after isolating organic acid producing strain in a liquid medium comprising the neutralized biowaste material as a sole source of saccharide, by making a color change in the culture medium suggesting pH reduction, as a parameter, and carrying out organic acid profile analysis of culture solution using HPLC;    (2) selecting microorganisms which produce specific optical isomers and using the microorganisms for succinic acid fermentation;    (3) producing a fertilizer, manure, soil improving material, probiotic formulation, health food, single cell protein (SCP) etc using the residue or fermented liquor produced by organic acid fermentation; and    (4) a method and apparatus for producing various organic acids other than succinic acid such as lactic acid, citric acid, malic acid, acetic acid, formic acid and propionic acid.