Magnetic disk device and magnetic recording medium

A magnetic disk device comprising:

• a magnetic recording medium in which one servo track and an array of at least two data tracks are formed alternately;
• a head portion including a set of reading heads arranged in a radius direction of said magnetic recording medium for reading signals from said magnetic recording medium;
• and
• a controller controlling a position of said head portion based on servo signals read from the one servo track and a second servo track on the other side of the array of data tracks, the servo tracks being read by the reading heads disposed at opposite ends of the set,
• wherein a pitch between the reading heads disposed at the opposite ends is narrower than a pitch between the servo tracks, and
• the reading heads disposed at the opposite ends are disposed so that an effective sensitivity region of one of the outermost reading heads reaches the center of the one servo track while an effective sensitivity region of the other outermost reading head reaches the center of the second servo track.