To provide a dressing device capable of efficiently reproducing a polishing surface, by surely and easily planarizing the polishing surface, even if the polishing surface on a polishing table has irregularity.

This dressing device 50 for dressing the polishing surface 35a on the polish table 35 for polishing an object W to be polished by sliding on the object W to be polished. This dressing device 50 has a dresser 51 formed in an elongated rectangle for dressing the polishing surface 35a. The dressing surface 51a of the dresser 51 is formed into a plane surface 51a-1 in contact with the polishing surface 35a, and taper surfaces 51a-2, 51a-3 inclined in a direction separating apart from the polishing surface 35a from the plane surface 51a-1 or the curved surfaces extending in a direction separating apart from the polishing surface 35a from the plane surface 51a-1.