This method can easily diagnose the disease progression of patients with Parkinson's disease. Provided is a method that uses, as a marker for determining Parkinson's disease, the count of at least one intestinal bacteria selected from the group consisting of Bifidobacterium, the Bacteroides fragilis group, Lactobacillus brevis and the Lactobacillus plantarum subgroup, and/or the total intestinal bacteria count. The method for determining Parkinson's disease uses, as an indicator, the blood LPS concentration and/or the blood LBP concentration of patients with Parkinson's disease.
