A ceramic porous body includes skeleton portions; and pore portions formed between the skeleton portions, the pore portions being capable of allowing a fluid to flow therethrough. In a cross section parallel to a flow direction of the fluid, the skeleton portions have a ratio of a skeleton length of 40 μm or more of 15% or less in a direction orthogonal to the flow direction of the fluid.

A pillar-shaped honeycomb structure body of a honeycomb structure includes a circumferential cell structure, a central cell structure and a boundary wall therebetween. On a surface orthogonal to the cells there are a circumferential reinforcing region having the partition wall thicker than a basic partition wall thickness in the circumferential cell structure and existing outside a range of a distance from a centroid of the surface; and at least one of a first boundary reinforcing region having the partition wall thicker than the basic partition wall thickness and existing in a range of a distance from the centroid within a range of the circumferential cell structure and a second boundary reinforcing region having the partition wall thicker than a basic partition wall thickness in the central cell structure and existing outside of a range of a distance from the centroid within a range of the central cell structure.

A pillar-shaped honeycomb structure filter including a plurality of first cells and a plurality of second cells, the first cells and the second cells being alternately arranged adjacent to each other with a porous partition wall interposed therebetween, wherein a ceramic porous film, in which an average film thickness T (unit: μm) is 2 to 50 μm, a porosity P (unit: %) is 65 to 90%, and the average film thickness T and the porosity P satisfy a relational expression of 0.36T+60≤P≤0.75T+72, is formed on a surface of each of the first cells.

A ceramic filter having a pillar-shaped honeycomb structure, wherein when observing a plurality of pores from a surface of partition walls with a laser microscope and plotting an equivalent circle diameter (μm) of each pore on an X-axis and a pore depth (μm) of each pore on a Y-axis on a two-dimensional coordinate system, a slope of a regression line (y/x) obtained by a least squares method in a range of 20≤x≤40 is 0 to 0.20, an average value of the pore depth of the plurality of pores is 2.5 μm to 5.0 μm, and a number density of the plurality of pores is 600/mm.sup.2 to 2450/mm.sup.2.

A honeycomb structure comprising a pillar-shaped honeycomb structure body having a porous partition wall disposed so as to surround a plurality of cells, wherein let that A denotes an absolute value of open frontal area (%) in a plane of the honeycomb structure body orthogonal to the extending direction of the cells and P denotes an absolute value of porosity (%) of the partition wall, the honeycomb structure has a value represented by the following expression (1) that is 0.05 to 0.12, let that D denotes an average pore diameter (m) of the partition wall and G denotes a geometric surface area (mm.sup.2/mm.sup.3) of the partition wall, the honeycomb structure has a value represented by the following expression (2) that is 8 to 50 (μm×mm.sup.2/mm.sup.3), and the honeycomb structure has a hydraulic diameter of the cells that is 1.1 mm or more,

(1−A/100)×(1−P/100),  Expression (1)

D×G.  Expression (2)

A method for producing a porous body, comprising a raw-material mixing step of mixing talc having an average particle size of 1 μm or more and 18 μm or less, alumina, an auxiliary raw material containing a material that undergoes a eutectic reaction with talc and being prepared in an amount so as to satisfy a weight ratio of 0.5% or more and 1.5% or less by weight relative to the talc, and a pore-forming agent, to provide green body, and a molding and firing step of molding the green body to provide a compact and firing this compact at a firing temperature of 1350° C. to 1440° C.

A honeycomb filter includes a plugged honeycomb structure body which has cell rows arranged along one direction in a cross section of the honeycomb structure body and including a first cell row in which at least the inflow cells are included and in which in the cross section perpendicular to the extending direction of the cells, a through channel area SA occupied by the inflow cells is larger than a through channel area SB occupied by the outflow cells, and a second cell row in which at least the outflow cells are included. A width P1 (mm) of the first cell row, a width P2 (mm) of the second cell row and a curvature radius R (μm) of a curved shape of corner portions of a polygonal shape of each cell satisfy a relation of Equation (1) below: Equation (1): 0.4≤(R/1000)/((P1+P2)/2)×100≤20.

Provided is an exhaust gas purification device that ensures an improved purification performance and a suppressed pressure loss. An exhaust gas purification device of the present disclosure includes a honeycomb substrate and an inflow cell side catalyst layer. disposed on a surface on the inflow cell side in an inflow side region of the partition wall. When a gas permeability coefficient of an inflow side partition wall portion including the inflow side region of the partition wall and the inflow cell side catalyst layer is Ka and a gas permeability coefficient of an outflow side partition wall portion including an outflow side region at least from the predetermined position to an outflow side end of the partition wall is Kb, a ratio Ka/Kb of the gas permeability coefficients is within a range of 0.4 or more and 0.8 or less.

A manufacturing method of a honeycomb filter includes a kneaded material preparation process, a forming process, and a firing process, wherein the cordierite forming raw material contains porous silica as an inorganic pore former, in a cumulative particle size distribution of the cordierite forming raw material, particle diameters (μm) of 10% by volume, 50% by volume, and 90% by volume of the total volume from a small diameter side, are denoted by D.sub.(a) 10, D.sub.(a) 50 and D.sub.(a) 90, respectively, and a particle diameter (μm) of 50% by volume of the total volume from the small diameter side is denoted by D.sub.(b) 50 in a cumulative particle size distribution of the organic pore former, and the cordierite forming raw material and the organic pore former satisfy given expressions.

A manufacturing method of a honeycomb filter includes a kneaded material preparation process, a forming process and a firing process, wherein the cordierite forming raw material contains at least one of porous silica and fused silica, particle diameters (μm) of 10% by volume, 50% by volume and 90% by volume, from a small diameter side, are denoted by D.sub.(a) 10, D.sub.(a) 50 and D.sub.(a) 90 in a cumulative particle size distribution of the cordierite forming raw material, and a particle diameter (μm) of 50% by volume from a small diameter side is denoted by D.sub.(b) 50 in a cumulative particle size distribution of the organic pore former, D.sub.(b) 50 is 40 μm or less, and a cordierite forming raw material and an organic pore former satisfy given expressions.