A linear motor comprises a stator module and a rotor module, wherein the stator module comprises a fixing seat and multiple magnetic pole pairs fixed on the fixing seat; each magnetic pole pair comprises two magnets; the rotor module comprises a sliding piece and a three-phase coil arranged in the sliding piece; the fixing seat comprises a supporting plate and two fixing plates connected with the supporting plate; two magnets in each magnetic pole pair are fixed on the two fixing plates respectively; the sliding piece is arranged between the multiple magnetic pole pairs on the two fixing plates; and air gaps are formed between the sliding piece and the multiple magnetic pole pairs on the two fixing plates. The linear motor also comprises two ball groups. The two ball groups are respectively located at two sides of the sliding piece. Each ball group is arranged between the side surface of the sliding piece and a corresponding fixing plate in a rolling mode. The air gaps between the rotor module and the stator module in the linear motor can be kept stably.