The purpose of this article is to propose introducing a marketing concept to Japanese public libraries for adapting to the outside environment. In the first part, marketing concept in public libraries is defined as a key concept to build a long-term relation with various stakeholders including customers and improve the effect on the whole society. Secondly, "public responsibility of libraries" is summarised as the basis of marketing in public libraries. One is to correct market failure from the viewpoint of economics, and the other is to contribute to the formation of public knowledge from the viewpoint of sociology. In the third part, the author advocates nich strategy as the optimal solution to such social expectation. Furthermore, the framework of competitive analysis aiming to understand the outside environment is suggested.
