The reliability of a semiconductor device is improved. Further, miniaturization of the semiconductor device is attained. A sealring is formed in a wiring structure provided over a semiconductor substrate. The sealring has a structure in which sealring wirings respectively formed in a plurality of wiring layers included in the wiring structure are laminated. The position of a side surface on the inner peripheral side of a sealring wiring formed in the wiring layer at the uppermost layer in the wiring layers is located more outside than the position of a side surface on the inner peripheral side of a sealring wiring formed in the wiring layer located one layer lower than the wiring layer at the uppermost layer. The width of the sealring wiring at the uppermost layer is smaller than the width of the sealring wiring located one layer lower than the wiring layer at the uppermost layer.