1. A noise reduction method, comprising: for each of multi-layer regions each containing a pixel of interest and having a successively reducing area, calculating a pixel statistic value of pixels in that region; for each of successive layers, correcting the pixel statistic value for a region at a current layer using a corrected pixel statistic value for a region at a preceding layer having a greater area than that of the region at the current layer; and correcting said pixel of interest using a corrected pixel statistic value for a region with a smallest area.