An eccentric vibration structure of electrical toothbrush includes an eccentric rod. Two ends of the eccentric rod are respectively formed with a transmission section and a weight section. The transmission section is drivable by a driving force to rotate so as to drive the weight section to eccentrically vibrate. The weight section has at least one weight part for partially or totally increasing the weight of the weight section, whereby due to the increased weight, the weight section is unbalanced in weight to deflect from a central axis of the eccentric rod.本發明提供一種電動牙刷的偏心振動結構，係包含一偏心桿，該偏心桿之兩端分別形成有一傳動部及一配重部，該傳動部受到一驅動力旋轉帶動該配重部產生偏心振動，該配重部具有至少一配重區用以增加該配重部的局部或全部重量，令該配重部藉由增加之配重產生配重失衡致偏離該偏心桿的一中心軸線者。
