Method for heat treating magnetic wire includes a wire supply unit, a wire property measuring unit, a wire tensile force measuring unit, a heat treatment unit, and a wire winding unit. The wire supply unit includes a supply bobbin, a supply rotary part, a wire reel, and a tension roller. The wire property measuring unit includes a size measuring device, an after measurement capstan, and a wire reel and measures a size of the wire prior to the heat treatment. The wire tensile force measuring unit includes a tensile force measuring device, a tension roller, and a wire reel. The wire heat treatment unit includes a heat treatment furnace, a temperature measuring device, an after heat treatment capstan, and a wire reel. The wire winding unit includes a winding bobbin, a winding rotary part that rotates the winding bobbin, a tension roller, and a wire reel.