An electric motor comprising: a yoke having a plurality of magnetic poles; a rotation shaft rotatably installed inside the yoke; an armature core having a plurality of teeth attached to the rotation shaft and radially extending in a radial direction, and a plurality of slots formed between the teeth; an armature coil wound on each of the teeth through an concentrated winding method; a commutator installed at the rotation shaft adjacent to the armature core and having a plurality of segments disposed in a circumferential direction; characterized in that it further comprises: an insulator configured to cover at least peripheries of the teeth and having an insulation property, wherein at least two armature coils, each of which comprises a first coil formed by winding a wire on the teeth from above the insulator in forward through the concentrated winding method and a second coil formed by winding the wire on the teeth from above the insulator in reverse through the concentrated winding method, are provided on the teeth, a partition section (166, 167) configured to determine a place at which at least one of a plurality of the armature coils are disposed is installed at the insulator, at least two accommodating portions (171, 172, 173) configured to accommodate the armature coil are formed on the insulator by the partition section (166, 167), the partition section (166, 167) being installed such that capacities of the accommodating portions (171, 172, 173) are substantially uniformized, and the first coil and the second coil being separately accommodated in each accommodating portion (171, 172, 173). a yoke having a plurality of magnetic poles; a rotation shaft rotatably installed inside the yoke; an armature core having a plurality of teeth attached to the rotation shaft and radially extending in a radial direction, and a plurality of slots formed between the teeth; an armature coil wound on each of the teeth through an concentrated winding method; a commutator installed at the rotation shaft adjacent to the armature core and having a plurality of segments disposed in a circumferential direction; characterized in that it further comprises: an insulator configured to cover at least peripheries of the teeth and having an insulation property, wherein at least two armature coils, each of which comprises a first coil formed by winding a wire on the teeth from above the insulator in forward through the concentrated winding method and a second coil formed by winding the wire on the teeth from above the insulator in reverse through the concentrated winding method, are provided on the teeth, a partition section (166, 167) configured to determine a place at which at least one of a plurality of the armature coils are disposed is installed at the insulator, at least two accommodating portions (171, 172, 173) configured to accommodate the armature coil are formed on the insulator by the partition section (166, 167), the partition section (166, 167) being installed such that capacities of the accommodating portions (171, 172, 173) are substantially uniformized, and the first coil and the second coil being separately accommodated in each accommodating portion (171, 172, 173). an insulator configured to cover at least peripheries of the teeth and having an insulation property, wherein at least two armature coils, each of which comprises a first coil formed by winding a wire on the teeth from above the insulator in forward through the concentrated winding method and a second coil formed by winding the wire on the teeth from above the insulator in reverse through the concentrated winding method, are provided on the teeth, a partition section (166, 167) configured to determine a place at which at least one of a plurality of the armature coils are disposed is installed at the insulator, at least two accommodating portions (171, 172, 173) configured to accommodate the armature coil are formed on the insulator by the partition section (166, 167), the partition section (166, 167) being installed such that capacities of the accommodating portions (171, 172, 173) are substantially uniformized, and the first coil and the second coil being separately accommodated in each accommodating portion (171, 172, 173).