Dermoid cyst which has several hypothesis of development is uncommon finding on the floor of the mouth. Recently the author has experienced one case of the dermoid cyst on the floor of the mouth. Surgically the cyst was removed completely with blunt dissection as intra-oral approach under general anesthesia. The cyst contained yellowish cheesy material surrounded with thin cystic wall. The cyst was diagnosed as dermoid cyst histopathologically.