Polishing apparatus and polishing method

A polishing apparatus comprising:

• a polishing table for holding a polishing pad having a polishing surface;
• a motor configured to drive said polishing table;
• a holding mechanism configured to hold a substrate having an object material to be polished and to press the substrate against the polishing surface, the object material belonging to one of a plurality of levels of a multi-level interconnect structure;
• a dresser configured to dress the polishing surface;
• and
• a monitoring unit configured to monitor a removal amount of the object material, said monitoring unit being operable to calculate the removal amount of the object material by quantifying a level number to which the object material belongs using a model equation containing a variable representing an integrated value of a torque current of said motor when polishing the object material, a variable representing a cumulative operating time of said dresser, and variables representing the level number to which the object material belongs and by substituting the cumulative operating time of said dresser and the integrated value of the torque current of said motor when polishing the object material into the model equation.