Honeycomb structured body

A pillar-shaped honeycomb structured body, comprising:

• a large number of through holes having two end portions that are longitudinally placed in parallel with one another with a partition wall therebetween,
• wherein said large number of through holes comprises a group of large-capacity through holes being sealed at one of end portions and a group of small-capacity through holes being sealed at the other end portion, the total areas of the large-capacity through holes on a cross section perpendicular to the longitudinal direction of the through holes is larger than the total areas of the small-capacity through holes on the same cross section;
• a catalyst;
• a partition wall A that separates two adjacent large-capacity through holes provided with a selective catalyst supporting portion used for selectively supporting the catalyst;
• and
• a partition wall B that separates a large-capacity through hole and a small-capacity through hole that are adjacent to each other,
• wherein the selective catalyst supporting portion comprises a protruded portion or a recessed portion or both on a surface of the partition wall A, the partition wall A having a thickness which varies along the protruded portion and the recessed portion, and the partition wall A supports a larger amount of the catalyst than the partition wall B.