To replace to one cell and one bit to reduce the memory capacity and to manage the coordinates of a beam spot position to form a two-dimensional code on a display face with high precision.

This method is constituted so that two-dimensional codes where the unit cells of a shade pattern are arranged like a matrix are formed on the display face by laser printing. It consists of a process where a bit map file is read in two preserve one cell of a bright or dark pattern as a '0' or '1' two-dimensional array, a process where the number of circular dots which will be put in one cell is calculated in accordance wit the size of one cell to be subjected to laser working and the diameter of circular dots formed by a laser beam on a material to be worked, a process where a working area is obtained in accordance with the preserved two-dimensional array and the size of one cell, a process where plural cell frames are set like a lattice with its center point as the reference, a process where circular dots are arranged in a cell frame at equal intervals, a process where beam spot coordinates corresponding to each of these arranged circular dots are preserved in a memory, and a process where working data preserved in this memory is outputted to a laser printer to perform marking on the display face.