An electromagnetic bandgap structure, including: a first metal layer; a first dielectric layer, stacked in the first metal layer; a metal plate, stacked in the first dielectric layer; a via, having one end part which is connected to the first metal layer; a second dielectric layer, stacked in the metal plate and the first dielectric layer; and a second metal layer, stacked in the second dielectric layer, whereas the other end part of the via is connected to a via land which is placed in a hole formed in the metal plate, and the via land is connected to the metal plate through a metal line.