Collapsing of decayed street trees by heavy rain or strong winds may threaten the safety of the people on street. In order to prevent the damage by falling street trees, survey of decayed street trees may be necessary. In this study, total of 155 street trees in Jeju were determined, whether they are infected by plant pathogen causing the decay. From the decayed tissues of the trees total 19 fungi were obtained. Among them, Fuscoporia senex, Ganoderma gibbosum, Vanderbylia fraxinea and Trametes versicolor were isolated. Especially, Vanderbylia fraxinea is one of the most dangerous mushroom, which is a white pathogenic fungus growing in a broadleaf tree for a year long.