Abstract: A carbon tube containing a carbonized tube wall. The tube wall is consisted of carbonized coating material and trace of fiber residue, and the carbonized coating material is prepared according to a process including the steps of: (a) coating a fiber structure with a carbon-containing coating material to form a coating layer over the fiber structure; (b) removing the fiber structure; and (c) carbonizing the coating layer to form the carbonized tube wall. The fiber structure can be either a two-dimensional or three-dimensional object, and a two-dimensional or three-dimensional device can be prepared accordingly.