A sealed honeycomb structure which can suppress increase of pressure loss and improve durability favorably is disclosed. A sealed honeycomb structure 100 including includes a honeycomb structure having porous walls dividedly forming inlet cells and outlet cells, an outlet side sealing portion, and an inlet side sealing portion, wherein an opening area of the inlet cell is larger than an opening area of an outlet cell on a cross-section of the honeycomb structure, wherein at least one outlet cell is a reinforced cell where a reinforcing part for reinforcing the outlet cell is formed at at least one corner portion at which the walls on a cross-section vertical to an extending direction of the cell cross each other, and wherein the inlet cell is a non-reinforced cell where the reinforcing part is not formed at all the corner portions at which the walls on the cross-section vertical to the extending direction of the cell cross each other.