Fibrous dysplasia is characterized by progressive replacement of normal bone elements by fibrous tissue. Diagnosis of FDTB is made by a combination of histologic and radiologic findings. Fibrous dysplasia involving the temporal bone is an unusual presentation, with the most common associated finding being conductive hearing loss and stenosis of the external auditory canal, seen in approximately 8% of patients. A 52-year-old man visited out-patient clinics due to left ear hearing disturbance & otalgia. Otoscopic examination revealed narrowing of the left EAC. TBCT, TBMR revealed crescent-like thickening of the tympanic and squamous parts of the left temporal bone with intact bony cortex & secondary narrowing of the left EAC. A diagnosis of fibrous dysplasia was made on the basis of these findings. In operation, fibrous lesion was seen at antrum & biopsy was proved fibrous dysplasia. ICWM c T1 (L), superior EAC reconstruction was done. After surgery, hearing disturbance improved and new EAC was kept patent. Although it is rare, fibrous dysplasia shows unique image findings and clinical behavior, and must be taken into consideration when evaluating an EAC bony mass.