1. A method of providing multi spectral Doppler images, the method comprising: displaying an ultrasound image of an object in a first region; setting a plurality of sample volumes in the displayed ultrasound image; obtaining a plurality of Doppler signals corresponding to the plurality of sample volumes; and tridimensionally displaying in a second region the multi spectral Doppler images that are generated based on the plurality of Doppler signals according to a z-axis of a 3D coordinate system having a x-axis, a y-axis, and the z-axis, wherein the multi spectral Doppler images include a first Doppler image selected, based on at a first point of time from a Doppler image corresponding to a sample volume from among the plurality of sample volumes and a second Doppler image selected, based on at a second point of time different from the first point of time, from the Doppler image, and wherein the first Doppler image and the second Doppler image are displayed at different positions of the z-axis of the 3D coordinate system.