Daiganji is a temple which was in charge of repairing and building Itsukushima Shrine from the Sengoku period to the Meiji period. Until now, it has been thought that Daiganji became involved with the Ouchi clan after 1541. However, it became clear that a letter to Daiganji by the magistrate of Ouchi was dated 1520. This revealed that the relationship between Daiganji and Ouchi dates back to before 1520 and the artizans responsible for repairing and building Itsukushima Shrine belonged to Daiganji in 1520. Ouchi had a strategy to separate the artisans who had the skills to build castles from the priests of Itsukushima Shrine and make them side with Ouchi. In this article, based on the relationship between Ouchi and Daiganji, we clarified what kind of repair work Daiganji did during the period when Ouchi ruled Itsukushima.