A generation unit generates data of a plurality of images whose scan time is different on the basis of an output of the probe. A calculation unit calculates a plurality of index values related to pressure of the probe against the tested body on the basis of a physical quantity changing with the strength of the pressure. A specifying unit specifies a first image, which corresponds to a first index value of the plurality of calculated index values, and a second image, which corresponds to a second index value, among the plurality of generated images. A display unit displays the specified first and second images side by side.