Abstract: A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall and a circumferential wall, wherein the partition wall and the circumferential wall are integrally formed product made of the same material, a porosity of the partition wall is 45 to 70%, when a material strength of the material constituting the partition wall is set to F [MPa], a thermal conductivity of the material is set to k [W/mL], a bulk density of the honeycomb structure body is set to ? [g/cc], a Young's modulus of the material is set to E [GPa], a thermal expansion coefficient of the material is set to ? [10?6/° C.], and in a section orthogonal to the extending direction of the cells of the honeycomb structure body, a difference in thickness of the circumferential wall is set to ?T [mm], P calculated by the following equation (1) is 3.0 or more.