To provide a grinding device and a grinding method for easily grinding a super-semispherical concave surface.

Since an oscillating mechanism 57 oscillates a grinding disk part 10 around the oscillating center PC arranged inside, i.e., on the -Z side from an opening OP, a super-semispherical concave surface SS deeper than a semi-spherical concave surface in a workpiece WP can be easily ground. In other words, the oscillating center PC of the grinding disk part 10 corresponds to the center of curvature of the concave spherical surface, and the arrangement thereof inside the opening OP means that the super-semispherical concave surface SS with the center of curvature being inside the opening OP can be ground.