To suppress the parallel resonance between power/ground planes on printed circuit boards, electromagnetic bandgap (EBG) structure can be applied. The open-stub EBG structure with two stubs in a unit cell is expected to miniaturize the cell size, expand the stopband and form multi-stopbands. In addition to, compare it with mushroom-type EBG structure and open-stub EBG structure with one stub through equivalent-circuit analysis, we established the design methodology to realize both stopbands of 2.4 GHz and 5.2 GHz. As a result, different lengths with two stubs led separate stopbands of 2.4 GHz and 5.2 GHz. Furthermore, we evaluated the difference of spiral stub length between the equivalent circuit model using characteristic parameters and electromagnetic simulation that requires the physical sizes.