A composite magnetic head comprising a DC-erasing head, which is slidably contact with a driving magnetic tape, and which DC-erases a servo band of the magnetic tape in such a manner that the direction of the magnetization of the servo band the servo band is directed towards one direction of the lengthwise direction of the magnetic tape; a servo writing head, which is slidably contact with the magnetic tape, and which writes a servo signal thereon so that the direction of the magnetization of the servo band is directed toward the reverse direction to the direction directed by the DC erasing head; and an AC-erasing head, which is contact with the magnetic tape, and which AC-erases the magnetization of the data band of the magnetic tape is disclosed. The servo writing head and the AC-erasing head are provided at downstream of the driving magnetic tape relative to the DC-erasing head, and the DC-erasing head, the servo writing head and the AC-erasing head are unified with each other.