According to the present invention, when measurement of a distance (fetal head biparietal diameter) on an ultrasonic image is started, a first mobile marker for designating a start point and a standard range display graphic are displayed. The standard range display graphic is a graphic that is centered on the first mobile marker and comprises two circular graphics having radii that are configured to be a lower limit and upper limit of a fetal head biparietal diameter standard range. A user can designate the start point while recognizing, via the standard range display graphic, an end point candidate range. Subsequently, an end point can be designated while recognizing the end point candidate range via a stationary standard range display graphic.
