According to the present invention, a displacement measurement unit (30) measures, on the basis of a reception signal corresponding to a tracking wave reception beam obtained from a reception unit (14), the displacement of a tissue inside a subject after the generation of a shear wave. A fluctuation detection unit (40) detects periodic displacement on the basis of the displacement measurement result obtained from the displacement measurement unit (30). A shear wave speed calculation unit (50) calculates the propagation speed of a shear wave in the subject on the basis of the measurement result obtained from the displacement measurement unit (30) and the detection result obtained from the fluctuation detection unit (40).
