A processing device includes: three linear guides disposed at three vertices of a triangle in plan view as viewed from a direction parallel to a first direction; a processing unit supported by the linear guides to lift and lower in the first direction; a feed mechanism that lifts and lowers the processing unit in the first direction; and a holding mechanism that holds a processing object below the processing unit, in which the processing unit supports a grindstone to face the processing object and includes a spindle unit that rotates the grindstone around a rotation center, a centroid of the processing unit is located inside the triangle, and when the grindstone is rotated, the grindstone passes through a position not overlapping a centroid of the triangle and passes through a position deviated from the centroid of the triangle toward a location where a force is applied to the processing unit.