The present invention relates to a method for simply diagnosing the progress of disease condition of a Parkinson's disease patient. Provided are a method for determining Parkinson's disease using the number of one or more intestinal bacteria selected from the group consisting of Bifidobacterium, Bacteroides fragilis group, Lactobacillus brevis, and Lactobacillus plantarum subgroup and/or the total number of intestinal bacteria as a marker, and a method for determining Parkinson's disease using the blood LPS level and/or the blood LBP level of a Parkinson's disease patient as an indicator.