Exemplary embodiments disclose a rotor of an electric motor and an electric motor using the same. The rotor includes a core which includes a plurality of protrusion portions which are arranged along an outer circumference of the core and protrude radially to an outer portion of the core, and a plurality of concave portions interposed between the protrusion portions; a plurality of permanent magnets which are respectively disposed at the plurality of concave portions; and a plurality of pole pieces which are disposed at the plurality of concave portions and at outer sides of the plurality of permanent magnets. A length of each of the plurality of pole pieces in an axial direction is shorter than a length of each of the plurality of protrusion portions in the axial direction.