Manufacturing steps for a cathode ray tube or a glass bulb for the cathode ray tube are controlled in such a manner that a two-dimensional matrix code 3 comprised of a plurality of dots is marked by laser in an outer side surface of a glass bulb 1, 5, the two-dimensional matrix code 3 containing the information which can identify individually glass bulbs, and the manufacturing steps are conducted by using a computer and the particulars specified by the serial information.