An ameloblastoma is a locally aggressive odontogenic tumour that commonly develops from the odontogenic epithelium within the jawbone. Here we present for the first time a case of a rare primary ameloblastoma in the middle ear cavity, along with some consideration of its treatment and a new classification. A 65-year-old woman presented with a left middle ear cavity tumour. Pathological examination led to the diagnosis of an ameloblastoma. We resected the tumour along with an extensive part of the middle ear mucosa, which made it difficult to have an adequate margin. It is recommended that the remaining bone be ground 2-3 mm beyond the visible margin after resecting the gross tumour. Therefore, several cases are treated with conservative surgery, including physicochemical treatment. This factor should be considered when designing treatment strategies as good alternatives in cases where resection with an adequate margin is difficult.