Provided is a linear motor capable of reducing cogging. The linear motor has a field magnet part 5 having a plurality of permanent magnets 21 arranged to form N and S poles alternately; a core 14 having a plurality of salient poles 14a, 14b and 14c arranged facing the field magnet part 5; and a three-phase coil 16 wound around the salient poles 14a, 14b and 14c of the core 14. At respective sides in the moving direction of an armature having the three-phase coil 16 and the core 14, auxiliary cores 18 made of a magnetic material are provided to sandwich the armature 10. The distance P1 between a center of each auxiliary core and a center of a center salient pole 14b is set to be substantially ¼×(2N+1)×a magnetic pole pitch between N poles of the field magnet part 5 (N: an integer equal to or greater than 1).