To provide an automatic polishing device for polishing a polishing object (sample) without generating a rugged surface, horizontally and economically.

The polishing object is automatically polished by being held between a first rotating plate and a second rotating plate arranged in parallel. The first rotating plate and the second rotating plate are constituted to rotate in opposite directions each other. The first rotating plate is constituted so as to perform a vertical motion and a revolving motion with the polishing object as a center. When the first rotating plate shields light from a polishing amount detecting sensor, rotation of the first rotating plate and the second rotating plate is automatically stopped.