A capacitor and a circuit board having the same are provided. The capacitor includes a substrate, an oxide layer, a second electrode, an insulating layer, a plurality of conductive sheets and a plurality of vias. The substrate includes a first electrode and a porous structure. The porous structure in at least of two distribution regions has different depths. An oxide layer is disposed on the surface of the porous structure. The second electrode is disposed on the oxide layer and includes a conductive polymer material. The insulating layer disposed on the second electrode has a third and a fourth surfaces. The fourth surface of the insulating layer is connected with the second electrode. The conductive sheets are disposed on the first surface of the first electrode and the third surface of the insulating layer and electrically connected with the corresponding vias according to different polarities.