Ainu is an indigenous people of Japan, and their language is in danger of extinction.If the language is to express cognition, any sentence in any language should be restricted in the four-dimensional structure of cognition, which may be the universal deep structure of sentence. The universal sentence structure based on the Einstein's four-dimensional structure of cognition has verified in Spanish in Sakai (2006, 2017c), in Japanese in Sakai (2011, 2017d) and in English in Sakai (2016, 2017e). This book is the English version of Sakai (2017a) to analyze the surface structure of the Ainu language and verify the deep structure at the same time.