Micropipe and step structures on 6H-SiC (0001) surface were investigated by an atomic force microscopy (AFM). On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. Step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the (0001) plane is large enough,step bunching of 15R-SiC can be observed.