The tropical storm moved away from Japan's eastern coast Wednesday after sweeping through at least five prefectures.
Police said 18 people died in Hyogo Prefecture, about 500 kilometers (310 miles) west of Tokyo, and one person was killed in neighboring Okayama Prefecture.
Two people died in Tokushima on the southwestern island of Shikoku.
According to Japan's meteorological authorities, Typhoon Etau was the ninth tropical storm of the season. Heavy rains, floods and mudslides destroyed several thousand homes and interrupted transport links in some regions of western Japan.
A Pacific typhoon or tropical storm is a tropical cyclone that forms in the northwestern Pacific Ocean. The peak season for typhoons runs from May to November, although they can occur at other times of the year as well.
At least 120 people reportedly died and hundreds are missing in Taiwan as Typhoon Morakot swept across the island last weekend, causing the worst flooding in half a century. The typhoon also claimed 22 lives in the Philippines.
