A miniaturized magnetic head which can reduce running torque of a disk driving motor while head-touch and penetration margin of the magnetic head remain effective. The magnetic head comprises a slider which slides on a flexible magnetic disk, a head core, integrally formed with the slider, to perform recording/reproducing of information on/from the flexible magnetic disk, and a groove, having a width of less than 0.4 mm, formed on a sliding surface of the slider, the groove extending in a tangential direction of the rotation of the flexible magnetic disk and reaching from one end of the slider to the other end of the slider.