To provide a honeycomb structure body with excellent durability in which a crack caused by a thermal stress is hardly generated at the time of use.

In the honeycomb structure body, a plurality of honeycomb segments 2 comprising a honeycomb structure having a large number of flowing holes partitioned by a partition wall and axially penetrated are joined by a plane parallel to an axial direction of the honeycomb segments 2 and are integrally formed. The honeycomb structure body includes the honeycomb segments 2 in which a heat capacity per unit volume at an outer periphery side part 6 of the honeycomb segment 6 is larger than a heat capacity per unit volume at a center part 8 of the honeycomb segment 2.