A motor comprising: a stator including: a stator core having: an annular stator yoke; a plurality of inner teeth projecting from the stator yoke toward inside along a radial direction; a plurality of outer teeth, in equal quantity to the inner teeth, projecting from the stator yoke toward outside along the radial direction; inner slots formed between each one of the inner teeth; and outer slots formed between each one of the outer teeth; a plurality of coils wound on the stator yoke between the inner slots and the outer slots, and coupled together in one of a three-phase star-shaped wire connection manner and a three-phase delta-shaped wire connection manner, an inner rotor confronting the inner teeth with an air-gap in between, and including an inner rotor yoke and an inner permanent magnet; and an outer rotor confronting the outer teeth with an air-gap in between, and including an outer rotor yoke and an outer permanent magnet, wherein the inner rotor is coupled to a rotary shaft to which the outer rotor is coupled, wherein the inner slots and the outer slots are in equal number "S", and the inner permanent magnet and the outer permanent magnet have poles in equal number "P", characterised in that the number of slots "S" is S=12 and the number of poles "P" is P=20, 28 or 44. a stator including: a stator core having: an annular stator yoke; a plurality of inner teeth projecting from the stator yoke toward inside along a radial direction; a plurality of outer teeth, in equal quantity to the inner teeth, projecting from the stator yoke toward outside along the radial direction; inner slots formed between each one of the inner teeth; and outer slots formed between each one of the outer teeth; a plurality of coils wound on the stator yoke between the inner slots and the outer slots, and coupled together in one of a three-phase star-shaped wire connection manner and a three-phase delta-shaped wire connection manner, an inner rotor confronting the inner teeth with an air-gap in between, and including an inner rotor yoke and an inner permanent magnet; and an outer rotor confronting the outer teeth with an air-gap in between, and including an outer rotor yoke and an outer permanent magnet, wherein the inner rotor is coupled to a rotary shaft to which the outer rotor is coupled, wherein the inner slots and the outer slots are in equal number "S", and the inner permanent magnet and the outer permanent magnet have poles in equal number "P", characterised in that the number of slots "S" is S=12 and the number of poles "P" is P=20, 28 or 44. a stator core having: an annular stator yoke; a plurality of inner teeth projecting from the stator yoke toward inside along a radial direction; a plurality of outer teeth, in equal quantity to the inner teeth, projecting from the stator yoke toward outside along the radial direction; inner slots formed between each one of the inner teeth; and outer slots formed between each one of the outer teeth; a plurality of coils wound on the stator yoke between the inner slots and the outer slots, and coupled together in one of a three-phase star-shaped wire connection manner and a three-phase delta-shaped wire connection manner, an inner rotor confronting the inner teeth with an air-gap in between, and including an inner rotor yoke and an inner permanent magnet; and an outer rotor confronting the outer teeth with an air-gap in between, and including an outer rotor yoke and an outer permanent magnet, wherein the inner rotor is coupled to a rotary shaft to which the outer rotor is coupled, wherein the inner slots and the outer slots are in equal number "S", and the inner permanent magnet and the outer permanent magnet have poles in equal number "P", characterised in that the number of slots "S" is S=12 and the number of poles "P" is P=20, 28 or 44. an annular stator yoke; a plurality of inner teeth projecting from the stator yoke toward inside along a radial direction; a plurality of outer teeth, in equal quantity to the inner teeth, projecting from the stator yoke toward outside along the radial direction; inner slots formed between each one of the inner teeth; and outer slots formed between each one of the outer teeth; a plurality of coils wound on the stator yoke between the inner slots and the outer slots, and coupled together in one of a three-phase star-shaped wire connection manner and a three-phase delta-shaped wire connection manner, an inner rotor confronting the inner teeth with an air-gap in between, and including an inner rotor yoke and an inner permanent magnet; and an outer rotor confronting the outer teeth with an air-gap in between, and including an outer rotor yoke and an outer permanent magnet, wherein the inner rotor is coupled to a rotary shaft to which the outer rotor is coupled, wherein the inner slots and the outer slots are in equal number "S", and the inner permanent magnet and the outer permanent magnet have poles in equal number "P", characterised in that the number of slots "S" is S=12 and the number of poles "P" is P=20, 28 or 44.