The present invention relates to methods of automatically determining and recognizing a code included in image data, and, more particularly, to a method capable of determining not only a one-dimensional code and a two-dimensional code but also a steganographic code with certainty.A code image processing method according to an embodiment of the present invention includes: a block extracting step of extracting a rectangular block unit area from image data; a block feature value calculating step of calculating the feature value of a code included in the rectangular block unit area; a block determining step of determining the type of the code included in the rectangular block unit area on the basis of the feature value of the code; and a code processing selecting step of selecting processing to be performed on the basis of the determined code type. According to the image processing method, it can be accurately determined whether a rectangular block unit area includes a steganographic code by using a steganographic feature value to determine the type of a code included in the rectangular block unit area.