A magnetic disk comprises an annular resilient magnetic recording mediumm, an outer ring having an outer affixing surface, and an annular frame disposed radially inwardly of the outer ring. The annular frame comprises an annular thrusting surface protruded axially for thrusting the recording medium to exert tension to it, an inner affixing surface inwardly affixed to the recording medium, and a base axially receded from the thrusting surface.