We investigated transformation of 4H-SiC etching shapes by high temperature annealing. Although the etching mask was circular, the etched shape resulted in a hexagon, dodecagon, or octadecagon, depending on the etching area size. A hexagon was transformed into a dodecagon along with the high temperature annealing, and a dodecagon was transformed into an octadecagon.Hexagon as well as dodecagon designed with different edge directions undergo different transformation by the annealing, owing to common preference of crystallographic faces. An edge corresponding to one of the {1-10x} faces appears as a straight line and seems most preferred. Edges corresponding to the {11-2x} faces also appear in a curvy feature, suggesting to be second most preferred. Faceted structures (bunching) were observed clearly on the {1-10x} faces but faintly on the {11-2x} faces. Therefore, it is necessary to design the shapes and their directions in an actual device in consideration of the transformation by annealing.