A circular columnar body made of ceramics and including a plurality of through-holes extending in a single axial direction Z and having circular or elliptical cross sectional shapes orthogonal to the axial direction at a density of 2 to 50 pieces per square inch in a cross section orthogonal to the axial direction is once hollowed out in a direction X orthogonal to the axial direction Z by a cylinder, and the circular columnar body can also be once again hollowed out in the direction orthogonal to the axial direction Z and the direction X by the cylinder.