The production method for an organic substance comprises: a step of feeding waste (G0) to a dryer (13); a step of drying the waste (G0) by the dryer (13); a step of feeding the waste (G0) dried by the dryer (13) to a gasifier (14); a step of gasifying the waste (G0) by the gasifier (14) to generate synthetic gas (G1); and a step of bringing the synthetic gas (G1) into contact with a microbial catalyst to generate an organic substance.