A honeycomb structured body of the present invention is a honeycomb structured body in which plural pillar-shaped honeycomb units are bonded to one another through sealing material layers, each unit having in the longitudinal direction a large number of cells placed in parallel with a cell wall therebetween. Herein, a cross-sectional area of the honeycomb unit on a cross-section perpendicular to the length direction is at least about 5 cm2 and at most about 50 cm2, the honeycomb unit includes inorganic fibers and/or whiskers in addition to inorganic particles, and a Young's modulus of the honeycomb unit is at least about 50% and at most about 150% of a Young's modulus of the sealing material layer.