In a feature data space including a first coordinate system that contains at least some of sets of feature data being respectively extracted for known specimens as its coordinate components an ultrasonic observation apparatus calculates coordinate values of the feature data of a specimen in a second coordinate system and assigns display parameters corresponding to the calculated coordinate values, wherein the second coordinate system has a new coordinate axis as one of its coordinate axes, the new coordinate axis is an axis on which sum of distances between adjacent representative points is large, the representative points represent respective groups obtained by classifying the known specimens on the basis of information regarding each known specimen, the distances are obtained when the adjacent representative points, which are adjacent along a predetermined coordinate axis in the first coordinate system, are projected on a predetermined axis.