A magnetic head has a main magnetic pole made of at least a magnetic material and a coil. The main magnetic pole has a stop layer through an inorganic insulating layer on both sides of the main magnetic pole in the widthwise direction. The boundary between the main magnetic pole and the metal layer becomes clear by the intervention of the inorganic insulating layer when viewing the flattened pattern plane by a scanning electron microscope and measuring the width of the main magnetic pole as a core width. The measurement accuracy of the main magnetic pole width can be improved and reductions in manufacturing yield rates which occur due to measurement errors can be prevented.