Abstract: An electric toothbrush having a circular front chamber and a rectangular rear chamber on the brush head thereof, a first brush holder and a second brush holder respectively mounted in the circular front chamber and the rectangular rear chamber, a transmission rod mounted inside the brush head and reciprocated by a DC motor drive, the transmission rod having a stub rod engaged into a guide groove on the bottom side of the second brush holder, and an upright pin inserted through a side notch on the first brush holder, wherein when the transmission rod is reciprocated by the DC motor drive, the second brush holder is forced to oscillate in the transverse direction, and the first brush holder is driven by the upright pin to move round about its own center.