To make a motor-driven toothbrush convenient to use for efficient brushing.

The motor-driven toothbrush comprises a body part 1 shaped for easy gripping by one hand while accommodating a motor 3 and a battery driving the motor 3, and a rod-shaped bed 2 removably attachable to an end of the body part 1 and having the bristles of the toothbrush at its end. A circular or ring-shaped inner brush 22 and a ring-shaped outer brush 23 are concentrically arranged on the head 2. The inner brush 22 is rotated by a first gear 21g leading to the rotating shaft 3a of the motor and by a second gear 22g engaging the first gear 21g. The outer brush 23 is rotated by a third gear 23g engaging the first gear 21g at a position different from the engagement position of the first gear for the second gear 22g. Two of the gears are positioned so that the two brushes arranged concentrically on the inside and outside rotate in opposite directions.