Although electroconvulsive therapy (ECT) is an effective treatment for schizophrenia, the treatment response rate is only approximately 50%. In addition, it is not clear what the optimal conditions are for maximizing ECT responsiveness. Meanwhile, an association between gut microbiota and the pathophysiology of schizophrenia has recently been reported. Therefore, we explored whether gut microbiota might predict the therapeutic efficacy of ECT. We examined the bacterial percentage of the gut microbiota of 11 patients with schizophrenia who received ECT treatment. Linear regression analyses showed that high Bifidobacterium and low Lactobacillus levels in stools before ECT were associated with a decrease in symptom severity, as measured by the Brief Psychiatric Rating Scale, after ECT. No bacteria showed significant changes in proportion before and after ECT. Our results suggest that Bifidobacterium and Lactobacillus levels could predict the responsiveness to ECT but not changes in the severity of schizophrenia.