There are disclosed embodiments for an ultrasound system for providing a color M mode image and a brightness M mode image. The ultrasound system comprises: an ultrasound data acquisition unit configured to perform a first operation for providing a first piece of ultrasound data for a color M mode image and a second operation for providing a second piece of ultrasound data for a brightness M mode image; a control unit configured to control the ultrasound data acquisition unit to perform the first operation by an average number of times and the second operation one or more times in a selective pattern within a predetermined sweep period to respectively accumulate the first pieces of ultrasound data and the second pieces of ultrasound data provided from the ultrasound data acquisition unit; and an image processor configured to form the color M mode image based on the accumulated first pieces of ultrasound data and to form the brightness M mode image based on the accumulated second pieces of ultrasound data.