Abstract: Provided is a method for producing an organic substance from a syngas by microbial fermentation, wherein only the solid component can be efficiently separated from an organic substance-containing liquid obtained by microbial fermentation to reduce the content of microorganisms, etc. Disclosed is a method for producing an organic substance from a syngas containing carbon monoxide by microbial fermentation, which comprises a microbial fermentation step wherein the syngas is fed to a microbial fermenting vessel and a liquid containing an organic substance is obtained by microbial fermentation, a solid-liquid separation step wherein the organic substance-containing liquid is separated into a solid component containing microorganisms and a liquid component containing an organic substance, and an extraction step wherein the organic substance-containing liquid is extracted from the liquid component, wherein the organic substance-containing liquid is heated to 40° C.