A bone mineral content measuring apparatus for obtaining the bone mineral content of an object to be examined by irradiating X-rays onto the object and measuring the X-rays which have passed through the object. An X-ray generating device generates X-rays having a continuous spectrum. The X-rays generated pass through an X-ray filter before the irradiation of the object or after the transmission of the object. The X-ray filter is composed of a substance having an X-ray absorbing characteristic with the K-absorption edge at a predetermined energy value. The X-rays which have passed through the X-ray filter and the object are detected by the X-ray detector. A data analyzer inputs the detected X-ray detection data and analyzes the bone mineral content of the object on the basis of the X-ray absorbing characteristic of the X-ray filter.