In forensic autopsies, postmortem microbial ethanol production makes it difficult to estimate the amount of antemortem alcohol consumption. 1-propanol, which is produced simultaneously with ethanol, has been used as an indicator of postmortem ethanol production. However, it becomes increasingly clear that postmortem ethanol production can occur without 1-propanol production. Therefore, the use of 1-propanol as an indicator of postmortem ethanol production is getting awkward to use and the identification of bacteria accompanied with ethanol production is required to elucidate the mechanism of postmortem ethanol production. In this study, we measured the blood alcohol concentration and analyzed the bacterial flora using the 16SrRNA (16S) gene region by next-generation sequencing to identify the bacteria involved in postmortem alcohol production. The bacterial flora analysis of 88 samples identified 1065 bacterial genera. Wed ivided the 88 samples into 3 groups as follows: Group Ⅰ(n=27); ethanol (-) and 1-propanol (-), Group Ⅱ (n=21); ethanol (+) and 1-propanol (-), and Group Ⅲ (n=40); ethanol (+) and 1-propanol (+). The bacterial content was compared among groups using Linear Discrimination Analysis Effect Size (LEfSe) and 16S copies. The total 16S copies was significantly larger in groups Ⅱ and Ⅲ than in group Ⅰ, demonstrating that postmortem alcohol production is more likely to occur as the bacterial content increases. In the blood of decomposed corpses, anaerobic bacteria such as Proteus and Vagococcus were involved in ethanol production, while Morganella, Peptoniphilus, Anaerosalibacter, and Tissierella were involved in 1-propanol production as well as ethanol production. This study demonstrated that the postmortem alcohol production depended on the amount and type of bacteria. This is the first study that analyzed the relationship between bacterial flora and alcohol production in cadaveric blood. These results may be applicable to the estimation of antemortem ethanol consumption in the practical forensic ...