A method renders volume data having multi-resolution. The volume data is divided into a plurality of sub-volumes according to a resolution, a sampling interval for each of the plurality of sub-volumes is determined based on resolutions of the plurality of sub-volumes, sub-volumes present in a path of a ray passing through each of pixels on a projection plane onto which the volume data is projected from one viewpoint are sampled according to the sampling intervals thereof, and a rendering value of each of the pixels on the projection plane is obtained by synthesizing a plurality of sampling values corresponding to each of the pixels from among sampling values obtained through the sampling.