In a feature data space in which it is possible to set a coordinate system having, as coordinate components, at least some of feature data that is extracted by performing approximation with respect to frequency spectrums of received ultrasonic waves, when a feature point of a frequency spectrum at a particular data position is present within a predetermined first type area in an i-th frame (where i is a positive integer) in a display unit and moves closer to a second type area, which has a lower priority for image display than the first type area, in subsequent (i+1)-th frame an ultrasonic observation apparatus generates feature-data image data by setting a virtual feature point at a position that is far off from the second type area as compared to the position of latest feature point and that is within or around the first type area, and by replacing visual information corresponding to the latest feature point in the (i+1)-th frame of the predetermined data position with visual information corresponding to the virtual feature point, and then displays the feature-data image data.
