Data reading apparatus

A dot code contains a plurality of data dots arranged according to the data to be recorded and markers providing data dot read reference points for reading the data dots and showing a predetermined relationship relative to the data dots in terms of a predetermined physical characteristic quantity, the data dots and the markers being arranged to show a predetermined positional relationship according a predetermined format. The parameter setting section determines parameters necessary for the marker detecting section to detect markers from the dot code image stored in the image data storage section. The parameters are determined on the basis of the relationship between the markers and the data dots in terms of the predetermined physical characteristic quantity in such a way that markers are detected firstly without detecting data dots.