<p>A honeycomb structure body (10) where honeycomb units are bound together, with seal material layers in between, and the honeycomb units each have through-holes arranged side-by-side oriented in the longitudinal direction with through-hole wall surfaces in between. The honeycomb units contain at least ceramic particles, and inorganic fibers and/or whiskers. The area of a cross section of a honeycomb unit orthogonal to the longitudinal direction of the unit is not less than 5 cm<SUP>2</SUP> and not more than 50 cm<SUP>2</SUP>, and ?1/?2 that is the ratio of the thermal conductivity ?1 of the honeycomb units to the thermal conductivity ?2 of the seal material layers is in the range of 0.2 - 5.</p>
