An electromagnetic bandgap structure and a printed circuit board are disclosed. In accordance with an embodiment of the present invention, the electromagnetic bandgap structure includes a mushroom type structure comprising a first metal plate and a via of which one end is connected to the first metal plate; a second metal plate connected to the other end of the via; a first metal layer being connected to the second metal layer through a metal line; a first dielectric layer, layer-built between the first metal layer and the first metal plate; a second dielectric layer, layer-built on the first metal plate and the first dielectric layer; and a second metal layer, layer-built on the second dielectric layer. With the present invention, it is possible to solve the aforementioned mixed signal problem by preventing the EM wave of a certain frequency range from being transferred.