A method for detecting a specific pattern contained in an image. The pattern-detection method has steps of binarizing the input image data to obtain binary image data, recognizing a partial image that is contained in the binary image data, is part of the specific pattern, and has an empty inside, and determining the specific pattern contained in the image based on the recognition results. In the partial-image recognition step, a pixel-block area of predetermined size containing a target pixel is successively scanned for the binary image data, and a partial image contained in the binary image data is recognized on the condition that at least one OFF-pixel exists within a reference block consisting of the target pixel and predetermined pixels in its neighborhood within the block.