A motor using Hall effect elements is disclosed, in which a disk-shaped multi-pole magnet which is circumferentially divided into a plurality of magnetic poles each magnetized in an opposite polarity to its adjacent magnetic poles is attached to a rotary shaft and a magnetic circuit is constituted by the multi-pole magnet and a yoke plate disposed to face the multi-pole magnet. A pair of Hall effect elements are disposed within a magnetic field of the multi-pole magnet to detect positions of the respective magnetic poles of the multi-pole magnet. Output voltages from the pair of Hall effect elements are supplied to a pair of drive coils, respectively, to generate driving magnetic fluxes therein. A pair of pole pieces are mounted on the yoke plate to face the pair of Hall effect elements, respectively. The pair of pole pieces are axially movable to allow adjustment of spacings between the respective pole pieces and respective Hall effect elements so that magnetic flux densities supplied to the pair of Hall effect elements can be adjusted.