A
honeycomb structure is disclosed that includes plural
honeycomb units bonded together by using a sealing material layer, each of the
honeycomb units including plural through-holes separated by plural partition walls and provided in parallel along a longitudinal direction. Each of the honeycomb units includes at least
ceramic particles, and inorganic fibers and / or
whiskers; a cross sectional area of the honeycomb unit is from about 5 cm2 to about 50 cm2; and an outer surface of each honeycomb unit and the sealing material layer satisfy: about 0.5≦κ / d×(dc / κc+df / κf)≦about 1, where, κf (W / mK) and df (mm) represent a
thermal conductivity and a thickness of the outer surface of the honeycomb units, respectively, κc (W / mK) and dc (mm) represent a
thermal conductivity and a thickness of the sealing material layer, respectively, and κ (W / mK) and d (mm) represent a
thermal conductivity and a thickness of the combination of the outer surface and the sealing material layer.