To secure a substrate grinding device and its method, capable of grinding the flatness of a substrate in an extremely highly accurate manner.

In a substrate grinding device, having a pad 4 held by a surface plate 3, a slurry feeder 5 dripping slurry 6, and a substrate holder holding a substrate 1, and making the pad 4 and the substrate 1 forcibly contact face-to- face with each other via the slurry 6 while making them relatively move, thereby grinding the substrate 1, it is provided with a pressing contact force controlling means which makes a pressing contact force of the substrate 1 to the pad 4 variable periodically. In this constitution, since this substrate is highly accurately flattenizable, this grinding device is able to meet the promotion of multilayer interconnection in a semiconductor device, and further a yield rate in this semiconductor device is well improvable. Likewise, the slurry is smoothly and uniformly diffusible over the whole grinding surface of the substrate, and since any sump of a reaction product is not produced there, the substrate can be ground into a highly accurate flat plane.