There is disclosed an embodiment for providing a change trend image. An ultrasound data acquisition unit transmits ultrasound signal to a target object and receives echo signal reflected from the target object to sequentially acquire a plurality of ultrasound data. A processor is connected to the ultrasound data acquisition unit. The processor sequentially extracts feature values from the plurality of ultrasound data, allocates colors corresponding to each feature value and forms a change trend image with the colors indicative of a change trend of the extracted feature values over time.