In this study, socialization of libraries in Medieval Europe has been examined by means of the growing of cities and movements of Ideologies. Cities, as results of economic based changes, caused the apperance of merchantiles in produce and consumption flows. Cities, by selecting an area outside of feudal city walls, and by consisting new living Habits which differances from village living Habits took its place in Medieval Feudal Regime. While cities consist their conceits, conceits consists the specialisatians which identifies the city from the village. Technologic developments, Innovations, the movements of different social classes, the changes in produce and consumption models, movements of Ideologies; carried Medieval Europe to Enlighment Period after very long and difficult experiements. While the man in "Enlighment Period" ideologically based on rationalism and critical thinking; it realized knowledge as a product of rationalism. That realisation gave start to the socialisation of libraries and books which include the "knowledge" stating with the innovation of press, the gobalization of books and the movements gave speed to the interactions and effected the extansion of knowledge in a positive way. While knowledge was socialized by means of the opportunities of cities, libraries became space which knowledge can easily reachable by society. Cities arosed in Middle ageesand by effecting social structures, they became an INDIRECT effect for reaching of libraries to society and moneyfree service. This study is explored in the context of the socialisation process of libraries in Medieval Europe, urban phenomenon and intellectual mobility. Cities; as an extension of the economic-based change processes of societies, it created the trader class in the production-consumption flow. Traders took their place in the Feodal Regime of the Middle Ages, with the formation of a new structure that differs from village life, supported by modern sociologists by choosing a place outside the walls. When creating urban institutions, institutions brought with them the characteristics that "city" separates from the 'country'. Technological advances, discoveries, class movements, change in production-consumption models, intellectual mobility, brought medieval Europe to the 'Ellinning Period' after long and demanding processes and experiences. "Knowledge" is a product of the mind in the thinking method based on the human, mind and critical approach of enlightenment. This approach initiated the process of socialising of the book and libraries in which information is in. The evolution of the book, which started with the invention of the printing press, and the urban mobility at that time accelerated intercultural interaction, which positively influenced the publication of information. While information is socialised in a sense, libraries have become places where information can be accessed more rapidly through the opportunities that cities offer. "Kent" was born in the Middle Ages and this long process has been an indirect factor in the public opening of libraries, free services of libraries, affecting social structures.