the present invention provides a reading or writing method and apparatus thereof for reading data on a medium or writing data thereon by reciprocatively driving a reading / writing head over the medium . the method comprises driving the head forward at a predetermined speed at all times , and returning the head at a predetermined maximum speed when the reading or writing length is at a maximum , or at a speed lower than the maximum speed when the reading or writing length is shorter than the maximum so as to complete the reciprocation of the head within the same period as when the reading or writing length is the maximum .