A honeycomb structure includes a ceramic block formed by a plurality of pillar-shaped honeycomb fired bodies each having a large number of cells longitudinally disposed in parallel with one another with a cell wall between the cells. The plurality of honeycomb fired bodies are combined with one another by interposing an adhesive layer with a sealing material layer formed on a peripheral face of the ceramic block and include a plurality of different shapes of the honeycomb fired bodies. A thickness of a peripheral wall forming the peripheral face of the ceramic block is virtually even. A shape of a cell located at an outermost periphery of the ceramic block is virtually identical with a shape of a cell located at a place other than the outermost periphery of the ceramic block. On the peripheral wall of the honeycomb fired body, a step is provided.