Henry David Thoreau, the most influential American writer, naturalist, philosopher in 19th century, who was also an important representative figure of the American Transcendentalism Movement, the outcast of social mainstream thoughts. For over 150 years, his thoughts have inspired people to seek a return to nature. As for his attitude towards life, he believed that human beings should live in their own way, listen to their own heart, and do what they believe is right. The purpose of this essay is to analysize Thoreau’s idea of Individualism and his involvement in the crucial social issues. The analysis will first consider the nature of individualism and make distinction between Thoreau’s individualism and individualism in American society. Then it will present an intensive study of Thoreau’s embracing of some notions of individualism in Civil Disobedience and Walden. And the effects of his individualism have given to society not only in America but in other countries.