PURPOSE: To easily obtain the bar code which appears when read and disappears after being read by sticking reversible thermal discoloring ink which decolors at room temperature, but colors when heated on the bar code.

CONSTITUTION: Reversible thermal discoloring ink which colors in purple above 60°C heating temperature is used as ink for printing the base 2 of the bar code 3 and reversible thermal coloring ink which colors in blue above 60°C heating temperature is used as ink for a symbol 1 such bars or a number. Those discoloring ink materials are both lightly green at room temperature. A hot blast is blown to the bar code 3 of a cosmetic article to which a bar code like this is attached from a hot blast blower provided nearby a handy type optical automatic reader to read the bar code 3. The bar code 3 after being read decolors at room temperature.