A motor that reduces a cogging torque and rotates at a high speed is presented. The motor comprises: a shaft, a plurality of core blocks coupled to the shaft, a plurality of permanent magnets inserted into each of the core blocks, and an aligning unit, coaxial with the shaft, and disposed between the shaft and the core blocks. The core block includes a plurality of core sheets each having at least a pair of flux barriers formed to be symmetrical to each other about a line of symmetry. A first rib lies along the line of symmetry and a separate anti-deformation rib is positioned within each of the pair of flux barriers. Accordingly, a skew process for a rotor is facilitated. An anti-deformation rib within the flux barrier provides structural integrity for the core block. Accordingly, when the rotor is rotated with a high speed, a bridge is prevented from being deformed.