1. A method of performing parallel box filtering in region based image processing, comprising: a first step of selecting parallel pixel blocks having a size of M×N to be operated in parallel; a second step of selecting pixels included in a mask region having a size of K×L that is a parallel pixel operation region and a first region having a size of (M+K−1)×(N+L−1) that corresponds to overlapping the M*N masks; a third step of selecting pixels of a second region commonly included in the mask regions of M*N and storing the results of operation with respect to the pixels of the second region as repeated operation values; and a fourth step of operating block operation values with respect to the parallel pixel blocks using the repeated operation values.