To provide a dental plaster cast processing device capable of executing the 'drilling process' and the 'grooving process' at the same time by one device, and capable of achieving a stable processing quality in the operation without any special skill.

The dental plaster cast processing device has a hole for inserting and fixing a pin on a flat bottom of a dental plaster cast and a groove around the hole. The device also has a drill for boring a hole and plural drills for grooving. The plural drills for grooving are disposed so that the tops of the drills project obliquely from a horizontal plane orthogonally crossing the drill for boring a hole.