A stepping motor comprising: a rotor assembly comprising a magnet and rotatably disposed around a rotation axis as center; and a stator assembly disposed around the rotor assembly and comprising two stator units which are axially coupled to each other and which each comprise a pair of yokes (23 and 28) and a winding to excite the pair of yokes (23 and 28), wherein the pair of yokes (23 and 28) each comprise an annular ring shaped base portion (24; 29) and a plurality of pole teeth (25; 30) bent up from an inner circumference (24a; 29a) of the base portion (24; 29) and are disposed such that each of the pole teeth of one yoke and each of the pole teeth of the other yoke are arranged alternately in a circumferential direction; wherein the pole teeth (25; 30) of the pair of yokes (23 and 28) each comprise a pair of slant sides (25a and 25a; 30a and 30a) which are inclined such that a width of the pole tooth (25; 30) decreases in accordance with an increase of distance from the base portion (24; 29), and in that at least a part of the slant side of the one yoke is located close to at least a part of the slant side of the other yoke ; wherein a ratio W2/W1 ranges from 0.2 to 0.8, wherein W1 is a maximum possible dimension of a slant side of a pole tooth projected on the base portion ; and W2 is a dimension of mutually opposing parts of adjacent slant sides of the pole teeth projected on the base portion ; characterized in that the ratio of a gap (G) formed between the slant sides of the pole teeth to the thickness of the pole teeth is between 0.15 and 0.25 and the thickness of the pole teeth is 0.8 mm. a rotor assembly comprising a magnet and rotatably disposed around a rotation axis as center; and a stator assembly disposed around the rotor assembly and comprising two stator units which are axially coupled to each other and which each comprise a pair of yokes (23 and 28) and a winding to excite the pair of yokes (23 and 28), wherein the pair of yokes (23 and 28) each comprise an annular ring shaped base portion (24; 29) and a plurality of pole teeth (25; 30) bent up from an inner circumference (24a; 29a) of the base portion (24; 29) and are disposed such that each of the pole teeth of one yoke and each of the pole teeth of the other yoke are arranged alternately in a circumferential direction; wherein the pole teeth (25; 30) of the pair of yokes (23 and 28) each comprise a pair of slant sides (25a and 25a; 30a and 30a) which are inclined such that a width of the pole tooth (25; 30) decreases in accordance with an increase of distance from the base portion (24; 29), and in that at least a part of the slant side of the one yoke is located close to at least a part of the slant side of the other yoke ; wherein a ratio W2/W1 ranges from 0.2 to 0.8, wherein W1 is a maximum possible dimension of a slant side of a pole tooth projected on the base portion ; and W2 is a dimension of mutually opposing parts of adjacent slant sides of the pole teeth projected on the base portion ; characterized in that the ratio of a gap (G) formed between the slant sides of the pole teeth to the thickness of the pole teeth is between 0.15 and 0.25 and the thickness of the pole teeth is 0.8 mm. <EOS>