Manufacturing method of plugged honeycomb structure

A manufacturing method of a plugged honeycomb structure having a plurality of cells defined by partition walls and forming through channels for a fluid, and plugging portions arranged to plug one of end portions of each of predetermined cells with a plugging material and plug the other end portion of each of residual cells with the plugging material, in accordance with a prescribed arrangement standard, the manufacturing method comprising a plugging material preparing step of mixing a ceramic raw material, a pore former, a thickener, an organic binder, a dispersing agent, and water and preparing the plugging material which is slurried, to form the plugging portions, wherein the plugging material preparing step comprises:

• a powder mixing step of mixing the ceramic raw material, the pore former, the organic binder and the dispersing agent each of which is constituted of powder, at predetermined blend ratios, a thickener mixing step of adding and mixing the thickener to a powder mixture obtained by the powder mixing step, and a kneading step of adding the water to a thickener added mixture obtained by the thickener mixing step, to perform kneading, wherein in the thickener mixing step, a total number of stirring revolutions of the powder mixture and the thickener is set to 500 times or less, and Page 2 of 8 the powder mixture and the thickener are in contact for 2 minutes or less during the thickener mixing step, wherein the thickener is polyethylene oxide.