PURPOSE: To correctly and surely read the bar code symbol printed paper or bar code symbol printed section in the cover of a product, which is stuck to the produce or the cover by means of a bar code reader to automatically classify products in a flow production process.

CONSTITUTION: A method in which a bar code symbol section 6 is pressed to a product 5 made by flow production and fixed to it by blowing air to the bar code symbol printed paper 7 stuck to the product 5 or the bar code symbol printed section in the cover 8 of the product 5, and a reading device equipped with a bar code reader 3 and a blower 4 on the one side of the bar code symbol reading section of a drive conveyor 1 for flow production. In the case of automatically classifying products in a flow production process, therefore, bar code symbols can correctly and surely be read by pressing the bar code symbol printed paper 7 or bar code symbol printed section 6 in the cover 8 to the bar code reader 3 by the air blow pressure of the simple and low cost blower.