Disclosed herein is a subwindow setting method for a face detector for detecting whether one or more facial images exist in each of subwindows having a set size while sequentially setting the subwindows in the width direction of an input image. A scan interval between two neighboring subwindows under consideration in the width direction is determined based on the facial color density of a first subwindow of the two neighboring subwindows. Further, a scan interval between the first and second rows in a height direction of the input image is determined based on the facial color density of the subwindows included in the first row.