When measurement of a circumference (abdominal circumference of a fetus) on an ultrasonic image is started, a first mobile marker for designating a major axis start point of an ellipse to be measured is displayed. After the major axis start point is designated, a second mobile marker for designating a major axis end point of the ellipse to be measured and a standard range display graphic are displayed. The standard range display graphic comprises two ellipses in which the major axis start point and second mobile marker constitute a major axis or minor axis and the circumferences are configured to be a lower limit and upper limit of the abdominal circumference. A user can designate the major axis end point while recognizing the positional relationship between the standard range display graphic and the outline of an abdominal cross section. Furthermore, a minor axis end of the ellipse to be measured can be designated using the standard range graphic as a guide.
