Sealed honeycomb structure and method of producing the same

There is provided a plugged honeycomb structure 1 including: partition walls 2 disposed so as to form a plurality of cells 3 extending from one end face 42 to the other end face 44 in the axial direction, and plugged portions 4 disposed so as to plug the cells 3 at one of the end faces, and a production method thereof. In this honeycomb structure 1, the plugged portions 4 and partition walls surrounding the plugged portions are unitarily formed. The production method includes a forming step, a plugging step for filling a plugging material, and a firing step. The plugging material contains solid particles capable of unitarily joining with at least one kind of solid particles contained in a forming raw material in a firing step. A ratio of a dimensional change (%)upon forming the partition walls out of the partition wall-forming material to a dimensional change (%) upon forming the plugged portions out of the plugging material is controlled to be within the range of 0.7% to 1.3 in the firing step. There is provided a plugged honeycomb structure having further improved strength, adhesion, and thermal shock resistance between partition walls and plugged portions and a production method thereof.