To provide a grinding apparatus which allows a footprint to be downsized.

A double wheel 35 is constructed by concentrically arranging a finishing grinding wheel 36 and a rough grinding wheel 37 having a larger diameter than the finishing grinding wheel 36. A diameter D1 of the finishing grinding wheel 36 is equal to or larger than a diameter d of a processed object 1, whereas a diameter D2 of the rough grinding wheel 37 is equal to or larger than the double of the diameter d of the processed object 1, and a difference between a radius R1 of the finishing grinding wheel 36 and a radius R2 of the rough grinding wheel is equal to or larger than a radius r of the processed object 1. The double wheel 35 is rotated and the processed object 1 is horizontally moved below the rough grinding wheel 37 to carry out rough grinding, and subsequently an outer periphery of the finishing grinding wheel 36 is positioned at a center of the processed object 1 having passed the rough grinding wheel 37, in order to carry out finishing grinding of the auto-rotating processed object 1 with the finishing grinding wheel 36.