The invention discloses a counter bore. The counter bore is formed in a thin part, and is composed of a bore and a countersunk head at one side of the bore, wherein at least one discharge slot is formed in the periphery of the bore in the radial direction; the discharge slot penetrates through the two surfaces of the thin part; and the discharge slot extends to the outside of the countersunk head in the radial direction. The discharge slot is used for releasing stress generated after blanking the counter bore, so that the two surfaces of the part are still kept flat, and therefore, component quality is improved.