In an electromagnetic bandgap structure including a plurality of conductive plates and a stitching via part, in which the plurality of conductive plates are placed on a first planar surface, the stitching via part includes a first via having one end part connected to one of the two conductive plates, a second via having one end part connected to the other of the two conductive plates, a spiral connector forming a spirally-shaped serial link structure on at least one vertical planar surface that is perpendicular to the first planar surface, a first conductive pattern connecting one end part of the spiral connector and the other end part of the first via with each other and a second conductive connecting pattern connecting the other end part of the spiral connector and the other end part of the second via with each other.