The present invention provides a mmode imaging method and apparatus for an ultrasonic diagnosis device to increase the continuity of the displayed mmode images. The mmode imaging method of the invention comprises steps: define a sample line on a frame of bmode image, so as to select bmode data of sample points constituting the sample line; convert the bmode data of the sample points obtained from two consecutive frames of bmode image into two of mmode lines arranged in time order in a mmode image; at predetermined positions between the two mmode lines, generate mmode data that constitute at least one mmode lines based on the echo data of corresponding sample points on the two mmode lines; and image the mmode data in time sequence.