PURPOSE: To make laying of bar codes easy on a tread face part and to improve processability by stamping a combination of long grooves with a triangular or semi-circular crosssection in the longitudinal and transverse directions on a part of the tread face part of a raw tire in cope with the kind of the tire.

CONSTITUTION: A base plate 6 equipped with each stamping punch 8 is lowered by actuating a press cylinder 7 of a stamping apparatus 3 on a tread W transferred under an unvulcanized state and apexes 8a and 8b of each stamping punch 8 where a code has been set in cope with a kind of the raw tire are pressed thereon. It is thereby possible to stamp a bar code Z with a code corresponding to a kind of a raw tire. This bar code Z is a long groove the crosssectional shape of which is triangular or semicircular. As the method for reading the bar code Z, the bar code Z with a recessed crosssection stamped on a part of the tread part W of the raw tire is read out by means of a television camera while illuminating apparatus 1a, 1b, 1c and 1d set on front, rear, left and right direction of the tread face part W are successively turned on or off.