A replacement brush for an electric toothbrush is provided which, by making the head thinner, makes the back teeth feel cleaner and which can diminish the unpleasantness caused by vibration in the buccal cavity. This replacement brush (1B) for an electric toothbrush includes a neck (3) detachably attached to a toothbrush body that includes the handle of the electric toothbrush, and a head (4). The maximum thickness (T) of the head (4) is 2-4 mm, the minimum thickness (D) of the neck (3) is 3-5 mm, the relation D ≥ T is satisfied, and, on the back surface side of the head (4) and the neck (3) on the side opposite of the front surface where the bristled surface (4a) is provided, the head (4) is provided biased in the direction from the back surface towards the front surface with respect to the neck (3).<；u/>； <；u/>；
