A bone disease evaluating system comprising a radiation source for emitting radiation toward an image subject including bones, a detector for detecting a radiation phase contrast image showing the phase contrast of radiation emitted from the radiation source and transmitted through the bones, a joint recognizing section for recognizing a joint of the bones from the phase contrast image, and a profile obtaining section for obtaining a shape profile showing the change of shape of the joint from the recognized joint and a frequency analyzing section for performing frequency analysis of the obtained shape profile and an index calculating section for calculating an index concerning a disease of the joint on the basis of the result of the frequency analysis.