The amplitude deviation of a tracking error signal in an optical disk apparatus is reliably corrected by processing signals at low costs. A servo signal generator generates a tracking error signal and a lens error signal from a photodetected signal. A lens error deviation signal memory circuit stores the lens error signal generated at the servo signal generator, and reproduces the one-turn deviation of the lens error signal. A tracking error signal corrector learns an amplitude correcting value for the tracking error signal from the tracking error signal detected in reproducing the one-turn deviation of the lens error signal, and stores the amplitude correcting value in a correcting signal generator.