For a three-dimensional region including a treatment target site of a patient, a puncture needle scanning region R1 having a slice thickness d1 is set with reference to a cross section (a puncture cross section) including an insertion direction of a puncture needle. Subsequently, in the y-direction substantially perpendicular to the puncture cross section, two treatment target scanning regions R2 (R21 and R22) each being adjacent to the puncture needle scanning region R1 and having a slice thickness d2 are set. Then, based on volume data in the puncture needle scanning region R1 acquired by first three-dimensional scan with ultrasound waves and volume data in the treatment target scanning regions R2 acquired by second three-dimensional scan performed at a lower volume rate than the first three-dimensional scan, image data is generated for the purpose of supporting puncture.