Lipoma is a benign lesion composed of fat tissue. It is a common neoplasm but rarely seen in oral cavity especially in floor of mouth. It is more common in male and seen most often after age of 40 years. The authors experienced a case of lipoma on floor of mouth. The tumor was completely removed out under general anesthesia. Histopathologic examination verified lipoma. So the authors report this case with brief review of literatures.