An error detecting apparatus includes: a reading device obtaining an image read signal by reading a two-dimensional code pattern, which includes information blocks having information and boundary patterns, the information pattern including first/second pattern images (PIs) corresponding to first/second PIs, respectively, in each reading range corresponding to a size≧a size of the information block. A reference point detecting device detects an intersection in the boundary pattern, as a block reference point (P, Q), from the image read signal; an extracting device extracts the first/second information data (ID), based on one portion of the first PIs and the second PIs belonging to an ID extraction area determined according to a position of the block reference point; an error detecting device detects whether any error in the extracted first/second ID based on another portion of the first/second PIs belonging to another area other than the ID extraction area.