The present invention provides a method for measuring an optimum seeking time and an inspection apparatus using this method capable of measuring and setting an optimum seeking time for inspection of a magnetic disk or magnetic head. The method samples average level differences of sector-wise read signals in positive and negative domains for one round of track and detects a minimum value H and a minimum value L among these differences. The method recalculates the seeking time while changing the settling time. After writing and reading test data, calculates a deviation DEV of average levels DEV=(H−L)/(H+L). The method is adapted to obtain a minimum one of the values of settling time having measured when the deviation DEV of average levels is equal to or less than a predetermined value as an optimum settling time or an optimum seeking time.