A brush used to contact with a commutator, includes a brush body which includes two opposite axial end faces and a protruding portion projecting from the brush body toward the commutator. The protruding portion includes a first surface, a second surface and at least two teeth. The first surface and the second surface are respectively adjacent to the two axial end faces. Angles formed between the first surface and the second surface and corresponding adjacent axial end faces are obtuse. The teeth is located between the first surface and the second surface, and extends generally along a circumferential direction of the commutator. The ratio of a total width of the at least two teeth in an axial direction of the brush to an axial height of the brush body is in the range of 0.25-0.75. An electric motor including the brush is also provided.