Primary hyperhidrosis is a disorder of excessive, bilateral and relatively symmetrical sweating occurring in the palms, soles and axillae regions without obvious etiology. There have been some reports of the epidemiology of primary hyperhidrosis abroad so far, but there has never been any research performed in Japan. We performed a questionnaire survey for people aged 5–64 years who agreed with the purpose of this study at 20 companies or schools, and received 5807 valid responses. From this survey, each prevalence could broken down into 5.33% for primary palm hyperhidrosis, 2.79% for primary plantar hyperhidrosis, 5.75% for primary axillae hyperhidrosis and 4.7% for primary head hyperhidrosis. Patients with severe symptoms were estimated to be approximately 616 000 for primary palmar hyperhidrosis and 2 239 000 for primary axillae hyperhidrosis in Japan. These findings reveal that many patients feel a decreased quality of life because of symptoms of hyperhidrosis every day. However, only 6.2% of the patients had visited medical institutions. Moreover, few patients take appropriate treatment even after visiting the hospital.