NOVELTY - Producing culture medium (bed soil) for cultivating undisinfected seedling, involves taking decomposable organic materials, inoculating microorganisms, completely stirring and mixing materials, creating an weakly acidic fermentation environment, suppressing activity of saprogenic bacteria or various microorganisms, performing fermentation, reducing significant generation of offensive odor resulting from activity of saprogenic bacteria or various microorganisms, and obtaining culture medium comprising organic material.    USE - The method is useful for producing culture medium (bed soil) for cultivating undisinfected seedling (claimed).    ADVANTAGE - The method produces culture medium that is easy to decompose, and is environmentally-friendly.    DETAILED DESCRIPTION - Method for producing culture medium (bed soil) for cultivating undisinfected seedling, involves taking decomposable organic materials, such as chaff and livestock farming discharge, and culture medium base material which uses decomposable organic materials such as rice bran, livestock excrement, domestic fowl excrement, as main raw material, adding acid having pH of less than 4, inoculating microorganisms, preferably lactic acid bacteria which is derived from grain, completely stirring and mixing materials, creating an weakly acidic fermentation environment, suppressing activity of saprogenic bacteria or various microorganisms, performing fermentation, reducing significant generation of offensive odor resulting from activity of saprogenic bacteria or various microorganisms, and obtaining culture medium comprising organic material which is easy to decompose, where (a) the fermentation is (i) anaerobic fermentation process, (ii) primary aerobic fermentation process, or (iii) ripening (secondary fermentation) process, (b) the fermentation is expressed and continued sequentially and continuously, and (c) at time of aerobic fermentation, harmful microbes such as various microorganisms and pathogenic microbe, are exterminated by maintaining fermentation at 70 degrees C or more for several days.