A circuit board according to an embodiment comprises: an insulation layer; a circuit pattern disposed on the upper surface or under the lower surface of the insulation layer; and a buffer layer disposed on at least one surface of the upper surface and the lower surface of the insulation layer, wherein the buffer layer includes carbon, nitrogen, and oxygen, the ratio of the nitrogen to the carbon ((carbon/nitrogen)*100) is 5 to 15, and the ratio of the oxygen to the carbon ((carbon/oxygen)*100) is 15 to 30.