Disclosed is an ultrasonic diagnostic apparatus capable of easily obtaining an ultrasonic image for the same position of the same target object at different points of time. The ultrasonic diagnostic apparatus includes a probe configured to obtain ultrasonic data for an arbitrary position inside a target object, an image generator to generate an ultrasonic image for the arbitrary position using the ultrasonic data, a reference member provided to be in contact with the target object to set a reference position in the target object, a marker disposed on one side of the reference member, a sensor disposed on one side of the probe and configured to obtain a positional relationship with the marker, and a position calculator configured to calculate a positional relationship between the reference position and the arbitrary position using the positional relationship between the marker and the sensor.
