The present invention relates to a method of improving a 3D ultrasound color Doppler image through a post-processing. A method of processing an ultrasound image, includes the following steps: a) recognizing a target object from an inputted ultrasound image based on an object recognition algorithm using connectivity of the target object; b) setting at least one object region by using the connectivity of the recognized target object; c) calculating a structure matrix by using voxel gradients of the object region; d) calculating a diffusion matrix from the structure matrix; and e) acquiring a processed ultrasound image by applying the diffusion matrix and the voxel gradients to the inputted ultrasound image.