This is a report of multiple myeloma occurred in the left mandibular body and skull. 66-year-old patient was referred to our hospital with a complaint of painful swelling on the left mandibular body area. The author diagnosed it as a multiple myeloma by the clinical examination, radiographic findings, laboratory findings and the histopathological findings. The purpose of this report is to aid in the diagnosis of multiple myeloma and to aid to differentiate it from malignant tumours. The characteristic features are as follows: 1. In clinical examination, painful swelling was observed in left mandibular body area. 2. In radiographic findings, radiograms showed relatively ill-defined radiolucency without sclerotic border in left mandibular body area. And also represented multiple punched-out radiolucency in the skull and pathologic fracture of vertebral body on lumbar 3 level. 3. In histopathologic findings, infiltration of abnormal plasma cells was observed. 4. In laboratory findings, decreasing of albumin/globulin ratio, hypercalcemia, renal impairment was observed, but we could not find the Bence-Jones protein in urin.