The present disclosure relates to an ultrasonic diagnostic apparatus for providing a combination of an ultrasound image and a color flow image. The ultrasonic diagnostic apparatus detects a color index of each of pixels in a color flow image and provides a contour image composed of contour lines. Here, each of the contour lines is formed by grouping and connecting pixels having the same color index based on the detected color indexes of the respective pixels and formed for at least one color index level. A diagnosis method of the apparatus is also disclosed.
