Abstract: An electric toothbrush is provided with a brush portion, a motor including a rotary shaft, a battery, which supplies the motor with power supply voltage, and an eccentric shaft, which rotates together with the rotary shaft. The eccentric shaft has a center of gravity located at a position deviated from an axis of the rotary shaft of the motor. An oscillation transmission mechanism transmits oscillations generated by the rotation of the eccentric shaft. An oscillation amplitude regulation circuit regulates an oscillation amplitude of the brush portion to be constant regardless of changes in the power supply voltage in a state in which the brush portion is free from external loads.