Sakae Tsunoyama was a former president of Wakayama University and one of the leading scholars in the new fields of economics in the late 20th century in Japan. He published two books on tea culture and the world history. One is The World History of Tea – the Culture of green tea and the world of black tea, published in 1980, and the other is Tea and the Culture of Hospitality, published in 2005. The former, which has been one of the best-selling books, explores the influence of the Eastern tea culture, especially that of Japan in the late 16th and 17th centuries, on the European lifestyle culture of the age and the world history thereafter. The latter focusses much on the feature of hospitality in Japanese tea culture typically observed in the practice of chanoyu. This paper aims at the investigation of the essential factors of the transition of his ideas between the two books based on the literature by the Europeans who visited Japan in the late 16th and 17th centuries, and the documents on the tea gatherings practiced by Sen no Rikyu in the days of Oda Nobunaga and Toyotomi Hideyoshi.