An ultrasonic diagnostic apparatus which can measure a time difference of motion between a plurality of sites of a cardiac muscle for the heart of a fetus is provided. On a tomographic image of the heart, a user sets a plurality of observation points. Each observation point is tracked, and a plurality of displacement waveforms representing a temporal displacement of the plurality of observation points are generated. A time difference between a plurality of representative points is calculated between the plurality of displacement waveforms. Such a time difference is displayed as a numerical value or as a graph. The representative point is a peak point, a zero-cross point, an inflection point, or the like. The plurality of observation points are set along conduction pathways in the heart for the electric signal.