This study clarified the knowledge transmission occurring through social relationships among producers of log-grown shiitake mushrooms in satoyama in Tsushima City, Nagasaki Prefecture, Japan. Satoyama is forest that has been used for human activities such as agriculture and collecting firewood, resulting in the formation of a unique ecosystem. However, the use of satoyama is decreasing and biodiversity is being damaged. Nevertheless, satoyama continues to be used for shiitake mushroom production in some regions. Two methods are mainly used to cultivate shiitake mushrooms in Japan: log cultivation, which has a relatively long history, and mushroom bed cultivation, which is the main method of producing shiitake mushrooms at present. Tsushima City is one the areas that continues to produce shiitake mushrooms by log cultivation. The purpose of this study was to clarify the sustainability of log-grown shiitake mushroom production in Tsushima City by examining the social relationships and transmission of knowledge among log-grown shiitake mushroom producers. Tsushima City, which is an island located between South Korea and Japan, is inhabited by many endemic species, and only log cultivation is practiced on the island. The research method used in the study was a semi-structured interview targeting people involved in shiitake mushroom production in Tsushima City. The survey revealed that the main types of social relationships are family relationships, relationships with neighboring producers, and connections through the shiitake production subcommittee. Through these relationships, producers exchange knowledge of producing shiitake mushrooms and cooperate in their production. The contents of the interactions based on each relationship are discussed in this poster presentation. The social relationships among producers revealed in this study are important for considering future changes in shiitake mushroom production in Tsushima City, and furthermore, changes in utilization of satoyama.