Polishing apparatus

A polishing apparatus for polishing a to-be-polished object comprising:

• a polishing head constructed to allow the to-be-polished object to be attached thereto,
• a polishing table which is arranged to face the to-be-polished object attached to the polishing head and constructed to be able to rotate, and
• a film thickness measuring system for measuring film thickness of a conductive film on the to-be-polished object which is polished by the polishing apparatus;
• wherein the film thickness measuring system comprises
• multiple sensor heads installed in the polishing table, wherein each sensor head comprises an eddy current sensor, and
• a controller;
• wherein the controller comprises
• an oscillator which creates a common clock signal for driving the eddy current sensors, and
• multiple control circuits installed to correspond to the multiple sensor heads, respectively, wherein each control circuit is constructed to create, based on the clock signal from the oscillator, a driving signal supplied to an eddy current sensor in a corresponding sensor head and process a measurement signal received from the eddy current sensor in the corresponding sensor head.