An electric motor comprising a yoke having a cylindrical part, four segment-type permanent magnets that are provided on an inner circumferential surface of the cylindrical part, and an armature that is roratably supported on an inner side in a radial direction of the yoke, wherein the permanent magnet is formed such that an outer surface and an inner surface have an arc shape, an arc center of the inner surface is further decentered toward a direction away from the permanent magnet along a thickness direction of a middle portion in a circumferential direction of the permanent magnet than an arc center of the outer surface, the armature comprises a rotation shaft, an armature core that is fixed to the rotation shaft, and a commutator which is provided on the rotation shaft so as to be adjacent to the armature core and in which a plurality of segments are arranged in a circumferential direction, and the armature core comprises six teeth which radially extend along a radial direction and around which a coil is wound and six slots that are formed between the teeth and that extend along an axial direction, characterized in that two grooves (31, 32) having a different groove width from each other are formed on a surface that faces the permanent magnet of the teeth throughout an entire axial direction of the rotation shaft, the teeth and the slots are formed to have a skew angle so as to diagonally extend with respect to the axial direction, when a decentering amount between an arc center of the inner surface and an arc center of the outer surface in the permanent magnet is δ, a polar arc angle of the permanent magnet is θ21, and the skew angle is θ2, the decentering amount δ, the polar arc angle θ21, and the skew angle θ2 are set so as to satisfy 0 mm < δ < 3 mm, 70 ° ≤ θ 21 < 80 ° and 0 ° < θ 2 ≤ 20 °, and the two grooves (31, 32) are formed to have the skew angle θ2. a yoke having a cylindrical part, four segment-type permanent magnets that are provided on an inner circumferential surface of the cylindrical part, and an armature that is roratably supported on an inner side in a radial direction of the yoke, wherein the permanent magnet is formed such that an outer surface and an inner surface have an arc shape, an arc center of the inner surface is further decentered toward a direction away from the permanent magnet along a thickness direction of a middle portion in a circumferential direction of the permanent magnet than an arc center of the outer surface, the armature comprises a rotation shaft, an armature core that is fixed to the rotation shaft, and a commutator which is provided on the rotation shaft so as to be adjacent to the armature core and in which a plurality of segments are arranged in a circumferential direction, and a rotation shaft, an armature core that is fixed to the rotation shaft, and a commutator which is provided on the rotation shaft so as to be adjacent to the armature core and in which a plurality of segments are arranged in a circumferential direction, and the armature core comprises six teeth which radially extend along a radial direction and around which a coil is wound and six slots that are formed between the teeth and that extend along an axial direction, six teeth which radially extend along a radial direction and around which a coil is wound and six slots that are formed between the teeth and that extend along an axial direction, characterized in that two grooves (31, 32) having a different groove width from each other are formed on a surface that faces the permanent magnet of the teeth throughout an entire axial direction of the rotation shaft, the teeth and the slots are formed to have a skew angle so as to diagonally extend with respect to the axial direction, when a decentering amount between an arc center of the inner surface and an arc center of the outer surface in the permanent magnet is δ, a polar arc angle of the permanent magnet is θ21, and the skew angle is θ2, the decentering amount δ, the polar arc angle θ21, and the skew angle θ2 are set so as to satisfy 0 mm < δ < 3 mm, 70 ° ≤ θ 21 < 80 ° and 0 ° < θ 2 ≤ 20 °, and the two grooves (31, 32) are formed to have the skew angle θ2.