The present disclosure relates to a method of encoding a three-dimensional image including a point cloud. According to an embodiment of the present disclosure, a method of encoding a three-dimensional image may include determining a spatial area in a three-dimensional space represented by the point cloud, projecting, onto a two-dimensional plane, a plurality of points included in the point cloud to generate a plurality of patches, determining at least one patch corresponding to the determined spatial area, down-sampling at least one patch according to a predefined rule, generating a two-dimensional image by packing the at least one down-sampled patch and the plurality of patches corresponding to areas other than the determined spatial area, and generating and outputting a bitstream including data in which the two-dimensional image is compressed and information related to the down-sampling performed to generate the two-dimensional image.