A signal-analysis portion executes a signal-analysis process to signal data that corresponds to an ultrasonic echo received from a subject. A determining portion determines whether image data regarding the subject, which is created based on the signal data upon which said signal-analysis process has been executed, includes a diagnostic target. A parameter-setting portion, based on the determination result, changes to a different value the value of a specific parameter that has an effect on the resolution of the signal-analysis process, among processing parameters to be employed in the signal-analysis process. A display portion displays image data regarding the subject based on the signal data that has been signal-analysis processed according to the specific parameter.
