It cannot be said that Francois Quesnay has ever developed a commercial theory deserving of the name. The reason why I am particularly interested in his reference to commerce is based on the fact that we can understand the general view of the Physiocrates regarding function and significance of commerce in economic circulation through his treatment of commerce. Quesnay, in his famous articles, "Du Commerce" etc., emphasizes the economic significance of "commerce." However, it must be remembered that his definition on commerce is sometimes broad or narrow in its meaning. In part I of the paper, the writer will consider the unproductivity of commercial industry for the reason that it does not produce "produit net." Therefore, agriculture is the fundamental industry of the country, where liberty and security are its chief requisites. In part II and III, Quesnay's view concerning commerce and price will be examined. He made a sharp distinction between commerce as a profit-making activity of merchants (le commerce revendeur) and pure commerce (le change qui se fait entre le vendeur de preiere main et acheture-consommateur.) Such a clear distinction as to commerce is expressed in the various parts of his works. And he put much stress upon the importance of the economic function which plays an active role in establishing "le bon prix." Lastly, the writer tries to make some additional remarks on Quesnay's explanation on the free play of commerce which is synonymous with free competition, while the mercantilistes believe that the country would be prosperous only by nationalism and state-regulation. Generally speaking Quesnay's analysis on commerce has a little Worth, theoretically, and his viewpoint about it has an important influence, even today, upon the establishment and development of the economic theory of commerce.