Honeycomb structured body and exhaust gas purifying device

A pillar-shaped honeycomb structural body comprising:

• a porous body having a plurality of through holes extending in parallel with one another in a length direction of the porous body and a wall portion interposed between said through holes, said plurality of through holes includes ones sealed at one end and ones sealed at the other end,
• wherein said plurality of through holes includes a plurality of large-capacity through holes opened on a flow-in side of said porous body and a plurality of small-capacity through holes opened on a flow-out side of said porous body, each of the large-capacity through holes has a relatively large area in a cross-section perpendicular to the length direction, each of the small-capacity through holes has a relatively small area in the cross-section, said large-capacity through holes and said small-capacity through holes have a substantially same number of through holes, said porous body satisfies relations, Y≦−1.1X+68.5, Y≦19, and 35≦X≦56, where Y represents a volume of said porous body in L and X represents an aperture ratio on the flow-in side in %.