Provided are a conditioner of a chemical mechanical polishing apparatus for polishing a substrate over a platen pad that rotates and a method thereof. The conditioner includes a disk holder, a piston rod, a housing, and a load sensor. The disk holder secures a conditioning disk that finely cuts a surface of the platen pad. The piston rod delivers a normal force to the disk holder. The housing covers at least a portion of the piston rod. The load sensor is installed to receive the normal force that the piston rod delivers to the piston rod and measuring the normal force.