A planar shape characteristic measuring apparatus and method, which can precisely and efficiently measure the characteristics relating to a surface shape of the measured surface of a disk such as a data recording surface of an optical disk including a laser Doppler speed meter which detects a perpendicular direction speed of a measured surface of a rotating disk; a tilt angle calculating unit which calculates a tilt angle in the rotational direction of an optical disk at each measuring position to a reference surface based on a linear speed at each measuring position detected by the laser Doppler speed meter and the detected perpendicular direction speed; a displacement calculating unit which calculates a perpendicular direction displacement of the optical disk at each measuring position; an acceleration calculating unit which calculates a perpendicular direction acceleration; and a focus servo error calculating unit which calculates a focus servo error which is predicted to occur in a focus servo system.