A honeycomb structure has porous partition walls for defining and forming cells communicating between two end surfaces of the structure and also has an outer wall formed integrally with the partition walls. The cells are composed of outermost peripheral partial cells and perfect cells. The outermost peripheral partial cells are located at the outermost periphery of the honeycomb structure and have imperfect cross sections, a part of each of which is in contact with the outer peripheral wall. The perfect cells are cells other than the outermost peripheral partial cells and have perfect cross sections. At one end of each of the outermost peripheral partial cells and of the perfect cells, there is formed a sealed section such that the entire surface of each end of the honeycomb structure has a checkered pattern of the sealed sections. The depth of the sealed sections in the outermost peripheral partial cells is less than that of the sealed sections in the perfect cells.