1. A method of analyzing elastography of tissue using ultrasound waves, the method comprising: inducing a shear wave on the tissue in a human body by Acoustic Radiation Force Impulse (ARFI) using an ultrasound probe having a two-dimensional (2D) transducer array; irradiating ultrasound waves using the ultrasound probe to acquire three-dimensional (3D) ultrasound data with respect to the tissue; acquiring the 3D ultrasound data using echo ultrasound waves of the ultrasound waves and a 3D volume acquisition method in which a 3D volume of the tissue is scanned by the 2D transducer array; calculating 3D displacement components of the shear wave in the tissue based on the acquired 3D ultrasound data; calculating a speed of the shear wave using the calculated 3D displacement components; calculating a shear modulus of the tissue using the speed of the shear wave; calculating a final shear modulus by calculating a mean value of the shear modulus in units of at least two frames in 3D ultrasound images; and displaying a 3D displacement map of the shear wave and a shear modulus map based on the final shear modulus.