A synchronous drive motor (SG, SG2) comprising: a stator (40, 240) including a stator core and windings, the stator core including a plurality of teeth that are spaced from each other by a slot formed therebetween with respect to a circumferential direction, the winding extending through the slot, each of the plurality of teeth including a portion wound with the winding; and a rotor including a plurality of permanent magnet parts, a back yoke part, and a plurality of auxiliary yoke parts (35, 235), the plurality of permanent magnet parts being arranged at intervals in the circumferential direction, each of the plurality of permanent magnet parts having a first magnet face facing the stator core and a second magnet face facing away from the stator core, the back yoke part supporting the plurality of permanent magnet parts, the back yoke part being provided opposite to the first magnet faces of the plurality of permanent magnet parts with respect to a direction in which the stator core and the first magnet faces are opposite to each other, the plurality of auxiliary yoke parts (35, 235) being provided to the back yoke part and arranged in the intervals, the plurality of auxiliary yoke parts (35, 235) being opposed to the stator core, each of the plurality of teeth including a distal end portion that is opposed to the first magnet face, the distal end portion having a smaller circumferential width than the sum of a circumferential width of the first magnet face and a circumferential width of a distal end surface of the auxiliary yoke part (35, 235), the number of the first magnet faces being more than the number of the teeth, wherein, in a surface of an innermost end of the auxiliary yoke part (35, 235), at least a part positioned most inward with respect to the radial direction is located inner than a center position that is a position centrally between the first and second magnet faces (37a, 37b) with respect to the radial direction, wherein a gap between the distal end portions of the teeth adjacent to each other with respect to the circumferential direction is larger than the circumferential width of the distal end portion. a stator (40, 240) including a stator core and windings, the stator core including a plurality of teeth that are spaced from each other by a slot formed therebetween with respect to a circumferential direction, the winding extending through the slot, each of the plurality of teeth including a portion wound with the winding; and a rotor including a plurality of permanent magnet parts, a back yoke part, and a plurality of auxiliary yoke parts (35, 235), the plurality of permanent magnet parts being arranged at intervals in the circumferential direction, each of the plurality of permanent magnet parts having a first magnet face facing the stator core and a second magnet face facing away from the stator core, the back yoke part supporting the plurality of permanent magnet parts, the back yoke part being provided opposite to the first magnet faces of the plurality of permanent magnet parts with respect to a direction in which the stator core and the first magnet faces are opposite to each other, the plurality of auxiliary yoke parts (35, 235) being provided to the back yoke part and arranged in the intervals, the plurality of auxiliary yoke parts (35, 235) being opposed to the stator core, each of the plurality of teeth including a distal end portion that is opposed to the first magnet face, the distal end portion having a smaller circumferential width than the sum of a circumferential width of the first magnet face and a circumferential width of a distal end surface of the auxiliary yoke part (35, 235), the number of the first magnet faces being more than the number of the teeth, wherein, in a surface of an innermost end of the auxiliary yoke part (35, 235), at least a part positioned most inward with respect to the radial direction is located inner than a center position that is a position centrally between the first and second magnet faces (37a, 37b) with respect to the radial direction, wherein a gap between the distal end portions of the teeth adjacent to each other with respect to the circumferential direction is larger than the circumferential width of the distal end portion.