The present invention is related to a health care instrument, particularly to a back sliding massager. The massager comprising a base, a slide consists of an upper and a lower plate, a transmission mechanism, massage heads, and a cover. In that, the slide, transmission mechanism, and massage heads are mounted into the chamber constructed by the base and cover. Chains disposed on the surface of the base, transmission mechanism installed between the cover and base includes a motor, a set of gears driven by the motor having bottom pinions meshed with the chains, each of top gears connected to one massage head on top of the cover by a central axle respectively; openings formed through the cover, massage heads are exposed out from the openings. The massager of the present invention has a larger massaged portion with a man-made massage effect.