Mandibular angle osteotomy is commonly used for prominent mandibular angle contouring. Because of difficult control of the line, shape, and amount of osteotomy, many complications such as asymmetry, undercorrection, overcorrection, and formation of a second mandibular angle after surgery occurred commonly. In addition, it is more difficult to implement osteotomy exactly the same as preoperative design in curved osteotomy owing to the arc-shaped osteotomy line. Therefore, further studies are needed to explore ways to make osteotomy accurately identical with preoperative design. In this report, a case of curved osteotomy guided by a stereolithographic template for unilateral prominent mandibular angle is described. We established the osteotomy line, the shape, and the volume with Mimics software for the right prominent mandibular angle; fabricated individual osteotomy template with computer-aided design/computer-aided manufacturing (CAD/CAM) technique; and performed curved osteotomy with the template. A secure fit of the template on the bone surface was found during the operation. Computed tomographic scan after the surgery revealed that bilateral mandibular angles were symmetric, that the right mandibular angle had a natural curve, and that the osteotomy line, shape, and amount were in accordance with the preoperative design. It is suggested that CAD/CAM template could guide curved osteotomy for prominent mandibular angle accurately, improve efficiency, and avoid complications in osteotomy.