To obtain a eggs or their products capable of individually giving information, such as their open dates, related to the eggs or the products on their storage, even when their packs are lost, by printing the open dates, etc., on the shells of the eggs with a printing ink comprising a food or a harmless edible substance.

Open dates, the dates of egg laying, egg gathering, production, processing, treatment or import, other information directly related to the open dates, the names of producers, etc., are directly printed on the eggs with a printing ink comprising a food or a harmless edible substance in a state not easily released. Eggs are preferably gathered in a fowlrun, washed, and subsequently printed with an ink jet printing printer, etc., before the eggs are packed for each desired number of the eggs.