There is provided a honeycomb structure 100 comprising partition walls 1 separating and forming a plurality of cells 2 functioning as fluid passages. The partition walls 1 are made of cordierite, and, when an average pore size of the partition walls 1 is x (μm) while a porosity of the partition walls 1 is y (%), a relation of x and y is y≦−8.33x+86.66 and satisfies 0.5≦x≦5 and 35≦y≦70. The honeycomb structure 100 can improve thermal shock resistance without sacrificing any of light-off performance, catalyst coatability, and strength.