Provided are a method and apparatus for automatically detecting a mid-sagittal plane of an object by using an ultrasonic image. The method includes obtaining an ultrasonic image for detecting the mid-sagittal plane detecting a face of the object from the ultrasonic image detecting a landmark from the detected face detecting landmark information which includes at least one of brightness and a form of the detected landmark and detecting a mid-sagittal plane of the object by using the landmark information.
