A carbon fiber has a coaxial stacking morphology of truncated conical tubular graphene layers, wherein each of the graphene layers includes a hexagonal carbon layer and has a large ring end at one end and a small ring end at the other end in the axial direction. When the carbon fiber is subjected to a heat treatment in a non-oxidizing atmosphere, the large ring ends of each two of the hexagonal carbon layers are linked by layer link sections in at least one of groups of the hexagonal carbon layers arranged in an axial direction, and an outer surface is closed to have a multi-semiring structure in cross section. When the carbon fiber is then subjected to a heat treatment in an oxidizing atmosphere, the layer link sections are released, whereby the edges of the hexagonal carbon layers are exposed at the large ring ends in a regularly arranged manner.