A stator (2, 120), comprising: a stator core that is placed so as to face in a radial direction a rotor core having a permanent magnet placed therein and that includes a plurality of teeth (21, 121) and a plurality of slots (22, 122) each located between adjacent ones of the teeth (21, 121); and a plurality of coils (30, 30a, 30b, 30c) placed in the slots (22, 122) of the stator core, wherein the plurality of teeth (21, 121) include a first tooth (21a, 121a) having the coils (30, 30a, 30b, 30c) of the same phase placed in the slots (22, 122) adjoining one side and the other side in a circumferential direction of the first tooth (21a, 121a), and a second tooth (21b, 121b, 131b, 141b) having the coils (30, 30a, 30b, 30c) of different phases placed in the slots (22, 122) adjoining one side and the other side in the circumferential direction of the second tooth (21b, 121b, 131b, 141b), a circumferential width of at least a part of such a portion of the second tooth (21b, 121b, 131b, 141b) that forms a magnetic path other than an opposing portion of the second tooth (21b, 121b, 131b, 141b) which faces the rotor core is smaller than a circumferential width of the first tooth (21a, 121a) at the same radial position, a groove (23, 23a, 23b, 123, 133, 143) is formed in a slot-side side surface of the tooth (21, 121) so as to extend in a rotation axis direction, the groove (23, 23a, 23b, 123, 133, 143) is not formed in the first tooth (21a, 121a) but is formed in the second tooth (21b, 121b, 131b, 141b), and a circumferential width of the second tooth (21b, 121b, 131b, 141b) at a radial position of a part of the second tooth (21b, 121b, 131b, 141b) which has the groove (23, 23a, 23b, 123, 133, 143) is smaller than a circumferential width of the first tooth (21a, 121a) at the same radial position, and the opposing portion facing the rotor core of the first tooth (21a, 121a) and the opposing portion facing the rotor core of the second tooth (21b, 121b, 131b, 141b) have substantially the same shape. a stator core that is placed so as to face in a radial direction a rotor core having a permanent magnet placed therein and that includes a plurality of teeth (21, 121) and a plurality of slots (22, 122) each located between adjacent ones of the teeth (21, 121); and a plurality of coils (30, 30a, 30b, 30c) placed in the slots (22, 122) of the stator core, wherein the plurality of teeth (21, 121) include a first tooth (21a, 121a) having the coils (30, 30a, 30b, 30c) of the same phase placed in the slots (22, 122) adjoining one side and the other side in a circumferential direction of the first tooth (21a, 121a), and a second tooth (21b, 121b, 131b, 141b) having the coils (30, 30a, 30b, 30c) of different phases placed in the slots (22, 122) adjoining one side and the other side in the circumferential direction of the second tooth (21b, 121b, 131b, 141b), a circumferential width of at least a part of such a portion of the second tooth (21b, 121b, 131b, 141b) that forms a magnetic path other than an opposing portion of the second tooth (21b, 121b, 131b, 141b) which faces the rotor core is smaller than a circumferential width of the first tooth (21a, 121a) at the same radial position, a groove (23, 23a, 23b, 123, 133, 143) is formed in a slot-side side surface of the tooth (21, 121) so as to extend in a rotation axis direction, the groove (23, 23a, 23b, 123, 133, 143) is not formed in the first tooth (21a, 121a) but is formed in the second tooth (21b, 121b, 131b, 141b), and a circumferential width of the second tooth (21b, 121b, 131b, 141b) at a radial position of a part of the second tooth (21b, 121b, 131b, 141b) which has the groove (23, 23a, 23b, 123, 133, 143) is smaller than a circumferential width of the first tooth (21a, 121a) at the same radial position, and the opposing portion facing the rotor core of the first tooth (21a, 121a) and the opposing portion facing the rotor core of the second tooth (21b, 121b, 131b, 141b) have substantially the same shape.