Graphitized 4H-SiC(0001) Si- and (000-1)C-terminated surfaces with an offset angle of 8° in the ultra high vacuum (UHV) are observed by scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). A network of string-shaped structures is developed on the Si-terminated surface after annealed at 1800°C. On the other hand, many protrusions corresponding to the ends of carbon nanotubes are generated on the C-terminated surface at the temperature. The network developed on the Si-terminated surface is composed of string-shaped structures along and perpendicular to step edges. The development of the network on the Si-terminated surface is investigated. It is found that string-shaped structures along step edges are generated at 1400°C, followed by the generation of that perpendicular to step edges at 1700°C. Models for the generation of string-shaped structures along and perpendicular to step edges are proposed. [DOI: 10.1380/ejssnt.2004.8]