A rotor assembly for a motor includes a rotor shaft having a journal portion formed in an axial direction and having a predetermined radius about an axis, and a center shaft portion extending along the axial direction from the journal portion and having a radius smaller than a radius of the journal portion about the axis; a cylindrical, integral permanent magnet inserted into the center shaft portion to surround an outer circumferential surface of the center shaft portion and being supported by the journal portion; and a sleeve inserted into the rotor shaft to surround an outer circumferential surface of the journal portion and an outer circumferential surface of the integral permanent magnet, supporting the integral permanent magnet in the axial direction, and supporting the outer circumferential surface of the center shaft portion in the radial direction.