To provide a motor-driven tooth brush capable of introducing fluorine ions into tooth, effectively exterminating bacteria and removing the element of plaque formation and plaque with one motor-driven tooth brush.

This tooth brush is provided with electrically conductive bristles on one side implanted to the brush part 2 of the tooth brush, electrically conductive bristles on the other side implanted by being insulated from these bristles, a control circuit 10 switching the polarity of voltage alternately applied to these conductive bristles, a grasping electrode 12 provided for a handle part 9 on a side opposite to the part 2 and a battery 11 supplying a power source for the conductive bristles through the circuit 10 and the electrode 12. In the case, plus is applied to bristles on one side at the former half of the applying of voltage, minus is applies to the bristles on the other side at the latter half of voltage, and a current flowing through these conductive bristles flows through a battery being the power source with a human hand.