NOVELTY - The method comprises forming oxidized carbon nanofibers from a carbon nanofiber material, performing thermal treatment of the oxidized carbon nanofibers to form a carbon nanofiber by separation of carbon nanofibers units, and reducing the separation of carbon nanofibers. In the formation of the carbon nanofibers, graphene layers are stacked perpendicular to a direction of a length of platelet-type carbon nanofiber. The oxidized carbon nanofibers are formed by humus substance method. The thermal treatment step is performed by microwave heat separation of the carbon nanofibers.    USE - The method is useful for manufacturing a carbon nanofiber (claimed) that is useful: in a super capacitor; and as electrode materials for energy storage devices such as fuel cells and a lithium ion battery; a catalyst carrier; and a conductive material for electrodes.    ADVANTAGE - The method allows manufacture of the one-dimensional carbon nanofiber with high specific surface area and excellent electrical conductivity, increased capacity and output characteristics and improved electrode resistance.    DETAILED DESCRIPTION - The method comprises forming oxidized carbon nanofibers from a carbon nanofiber material, performing thermal treatment of the oxidized carbon nanofibers to form a carbon nanofiber by separation of carbon nanofibers units, and reducing the separation of carbon nanofibers. In the formation of the carbon nanofibers, graphene layers are stacked perpendicular to a direction of a length of platelet-type carbon nanofiber. The oxidized carbon nanofibers are formed by humus substance method. The thermal treatment step is performed by microwave heat separation of the carbon nanofibers. The separation of the carbon nanofibers is carried out by ultrasonic treatment using a synchronizer. Each of the graphene layers is connected to the carbon nanofibers units. The reducing is performed using a reducing agent under an inert atmosphere or a reducing atmosphere containing a certain amount of hydrogen to improve conductivity of the carbon fiber. The heat treatment is performed at a temperature of 200 degrees C. The graphene layers are connected to each other as a graphene unit adjacent to carbon nanofiber unit. The carbon nanofiber unit has a thickness of 30-100 nm.