A linear motor includes a stator and a rotor. The stator includes two opposing plates, a spacing plate positioned between the plates, and a plurality of permanent magnets mounted on the two plates and spaced from each other. The rotor includes a coil portion and an assembly block. The coil portion is positioned between the two plates, and the assembly block is connected to the coil portion and next to the plates. The spacing plate defines a slide groove, and the coil portion includes a plurality of balls mounted at one surface toward the spacing plate. The plurality of balls is partially received in the slide groove in the sliding way.