[Problem] To be able to assess bone quality with a simpler examination. [Solution] According to the present invention, a subject's bone quality is assessed on the basis of an X-ray image of the subject's mandible, more specifically, on the basis of the variance in density of an assessment region 60 that includes an alveolar bone 36 portion surrounding a first molar premolar 30. The aforementioned X-ray image is obtained, for example, during a dental examination. One known example from the prior art for assessing bone quality, meanwhile, is based on X-ray images from DXA. That is to say, bone quality can be assessed by a simpler examination according to the present invention than the prior art that assumes that DXA, which is a relatively elaborate examination, would be performed. According to the present invention, bone density is also assessed, in addition to the assessment of bone quality. The risk that the subject will experience an osteoporotic fracture, i.e., the bone fracture risk, is also assessed on the basis of the results of the bone quality and bone density assessments.