The present invention provides an ultrasound diagnostic apparatus capable of appropriately evaluating dynamic characteristics of a bone. The ultrasound diagnostic apparatus obtains an interpolated line 52a representing a bone surface shape based on echo signals obtained from ultrasonic beams transmitted to a surface of the bone on which a load is applied. A user inputs an outer diameter φ of the bone which can be stored in a memory. The ULTRASOUND DIAGNOSTIC APPARATUS calculates a distortion ε which represents an expansion/contraction rate in an axial direction on the bone surface to which the load is applied, based on the interpolated line 52a and the bone outer diameter φ. The distortion ε is equal to a ratio defined by x/(x+dx)=r/(r+dr)=r/(r+1/2φ), wherein x represents a length of the bone surface in a measurement range (i.e., length of the interpolated line 52a) and x+dx represents a length of a neutral axis 52b of the bone.
