An optical recording sheet includes a plurality of data columns consisting of optical recording dots arranged in a matrix shape and column markers corresponding to the data columns. The data columns and the column markers of the optical recording sheet are detected by an optical line sensor and stored in a memory. On the basis of information stored in the memory, a marker detector detects the column marker and then two memory coordinates having a position known relative to the column marker are calculated. From the two memory coordinates, an inclining angle detector calculates the inclining angle between the optical recording sheet and the optical line sensor. On the basis of the memory coordinates and the inclining angle, an address calculator restores the optical recording dots stored in the memory coordinates.