A honeycomb structure includes a ceramic block and a sealing material layer. The ceramic block includes a plurality of honeycomb fired bodies each having a large number of cells longitudinally disposed substantially in parallel with one another with a cell wall between the cells, an adhesive layer for bonding side faces of the honeycomb fired bodies, and a cavity-holding member placed between the side faces of the honeycomb fired bodies. The sealing material layer is formed on a peripheral face of the ceramic block. The cavity-holding member includes a nonflammable material and has Young's modulus of at least about 0.001 GPa and at most about 0.07 GPa.