Hitherto Ryokan has been regarded as a man of many eccentricities, and a good calligrapher and an excellent poet as well. But his true value lies in the fact that he was a priest of Zen in its true sense. He performed his religious practice in complete self-renunciation, so that he was able to live in a true freedom of mind. I tried, in this article, to investigate the essence of Buddhism represented in the doctrine of Zen Patriach Dogen, following the deep intention of Ryokan's thinking among his calligraphs and poems which reveal his religious enlightenment.