A metal honeycomb structure (11) includes planar and corrugated sheets (15, 16) brazed together at first and second joining portions (17A, 17B) made of brazing materials applied to the corrugated sheet (16). The first and second joining portions (17A, 17B) are located proximate exhaust inlet and outlet (21, 22) of the honeycomb structure (11). The honeycomb further includes a joining strip (18) joined to a metal outer tube (12). The joining strip (18) is made of a brazing material (25) applied to an inner wall of the metal outer tube (12). The second joining portion (17B) overlaps the joining strip (18) and has a brazing length larger than a brazing length of the first joining portion (17A) which does not overlap the joining strip (18).
