This invention is intended to provide an identifiable bullet which is unduplicatable by a third party.The means is to place plural (two or more) kinds of identification codes onto or into a bullet and to make the identification codes mutually related. By this means the bullet remains identifiable. Next, the means is to make at least one kind of the identification code or codes ciphered. By this means the mutual relations among the identification codes become confidential to a third party, so that the bullet becomes unduplicatable.In one embodiment, each identification code is placed in a different kind of material, and this enables an investigator to detect and compare the identification codes more easily after shooting of the bullet.In another embodiment, each kind of identification code or codes is placed in a different kind of material.