A honeycomb structure comprising: a plurality of honeycomb segments each having porous partition walls with which a plurality of cells extending from one end surface to the other end surface are formed to become through channels of a fluid, and plugged portions arranged in open frontal areas of the predetermined cells in the one end surface and open frontal areas of the remaining cells in the other end surface, the honeycomb segments being arranged adjacent to each other so that side surfaces of the honeycomb segments face each other; joining portions in which the facing side surfaces of the plurality of honeycomb segments are joined to each other; and an outer peripheral wall which covers an outer peripheral surface of a honeycomb structure section constituted of the plurality of honeycomb segments and the joining portions, the honeycomb structure having an aspect ratio (a long axis/a short axis) of 1.2 or more, in which the long axis (L L) is the longest portion on each of the end surfaces of the honeycomb structure, and the short axis (L S) is the longest portion orthogonal to the long axis on the end surface, wherein corners which are regions of the joining portions in the region of 10 mm or less from each intersection between the joining portion and the outer peripheral wall along a direction of the short axis (L S) are present in the region of 25 mm or less from a straight line (C L) which passes through the center of the long axis (L L) and is parallel to the short axis (L S), and a thickness of each of the joining portions including the corners present in the region of 25 mm or less from the straight line which passes through the center of the long axis and is parallel to the short axis is 0.5 mm or more and 5 mm or less, and a thickness of each of the other joining portions is 1.5 mm or less, and characterized in that the thickness of each of the other joining portions is smaller than the thickness of each of the joining portions including the corners present in the region of 25 mm or less. a plurality of honeycomb segments each having porous partition walls with which a plurality of cells extending from one end surface to the other end surface are formed to become through channels of a fluid, and plugged portions arranged in open frontal areas of the predetermined cells in the one end surface and open frontal areas of the remaining cells in the other end surface, the honeycomb segments being arranged adjacent to each other so that side surfaces of the honeycomb segments face each other; joining portions in which the facing side surfaces of the plurality of honeycomb segments are joined to each other; and an outer peripheral wall which covers an outer peripheral surface of a honeycomb structure section constituted of the plurality of honeycomb segments and the joining portions, the honeycomb structure having an aspect ratio (a long axis/a short axis) of 1.2 or more, in which the long axis (L L) is the longest portion on each of the end surfaces of the honeycomb structure, and the short axis (L S) is the longest portion orthogonal to the long axis on the end surface, wherein corners which are regions of the joining portions in the region of 10 mm or less from each intersection between the joining portion and the outer peripheral wall along a direction of the short axis (L S) are present in the region of 25 mm or less from a straight line (C L) which passes through the center of the long axis (L L) and is parallel to the short axis (L S), and a thickness of each of the joining portions including the corners present in the region of 25 mm or less from the straight line which passes through the center of the long axis and is parallel to the short axis is 0.5 mm or more and 5 mm or less, and a thickness of each of the other joining portions is 1.5 mm or less, and characterized in that the thickness of each of the other joining portions is smaller than the thickness of each of the joining portions including the corners present in the region of 25 mm or less.