A sealed honeycomb structure may include porous walls dividedly forming inlet cells and outlet cells extending from an end surface of an inlet side to an end surface of an outlet side, an outlet side sealing portion, and an inlet side sealing portion, wherein at least one outlet cell is a reinforced cell, where a reinforced 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 reinforced 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.