A brushless DC motor includes a plurality of permanent magnet segments arranged on an outer circumferential surface of a yoke member. Each of the permanent magnet segments includes a thinnest portion positioned in a circumferential center portion of each of the permanent magnet segments, thickest portions positioned in circumferential opposite end portions of each of the permanent magnet segments, and gradually changing portions positioned between the thinnest portion and the thickest portions. The gradually changing portions have a thickness gradually increasing from the thinnest portion toward the thickest portions. A border between the magnetic poles is positioned in the circumferential center portion of each of the permanent magnet segments.