A method and an apparatus for compressing the three-dimensional data of a point cloud are disclosed. The present invention comprises, identifying a plurality of points constituting a point cloud, and projecting the plurality of identified points onto a projection plane so as to generate a projection image, wherein the bit number of projection points corresponding to the plurality of points projected in the projection image is determined on the basis of the distance between a first point closest to the projection plane and a second point farthest therefrom, on a normal with respect to the projection plane, among the plurality of points and/or on the basis of the number of intermediate points located between the first point and the second point.