A quadrangular or rectangular area on a medium surface of a printed material is defined as a block. A straight line in a vertical direction and a horizontal direction along an edge of the block is defined as a reference lattice line. A virtual lattice point is disposed at a predetermined interval on the reference lattice line. A reference lattice point dot is disposed on a virtual lattice point on a horizontal reference lattice line. A straight line connecting the reference grid point dots and virtual lattice points on a vertical line is defined as a lattice line. A point of intersection between lattice lines is defined as a virtual lattice point. A dot pattern is generated by arranging one or more information dots having a distance and a direction on the basis of the virtual lattice point. Such a dot pattern is scanned as image information by an optical reading means. Then, the dot pattern is converted into a numerical value and the information corresponding to the numerical information is read from a storage means. Then the information is outputted.