There have been various methods of reduction mandibular angleplasty. 21-year old woman with prominent mandibular angle and body was done curved angle ostectomy with tangential ostectomy. In operation, we had used bone wax for controlling of bone bleeding. After 1 year, the patient revisited to our clinic because she had a mass with tenderness on Lt. mandibular angle area. The mass had been gradually increasing in severity after reduction mandibular angleplasty. Computed tomography of the patient showed inflammatory lesion in Lt. mandibular angle area with focal cortical bony destruction and adjacent soft tissue thickening. After surgical removal of mass, clinical pathology revealed that the mass was chronic inflammatory fibrosis around foreign body(bone wax). The postoperative course was uneventful, the patient was satisfied for her shape. If possible we must avoid using a bone wax in reduction mandibular angleplasty, because bone wax can induce inflammatory reaction and fibrosis.