A honeycomb structure includes aluminum titanate and cell walls. The cell walls extend along a longitudinal direction of the honeycomb structure to form a plurality of cells between the cell walls. A porosity of the honeycomb structure is from about 40% to about 60%. In a binary image of substrate portions and pore portions of each of the cell walls, an area ratio (%) of the pore portions to a whole area in a rectangularly-divided image is in a range from (the porosity−about 25%) to (the porosity+about 25%). The binary image is converted from a microscopic image of a cross section of each of the cell walls in parallel with the longitudinal direction. The rectangularly-divided image is formed by dividing the binary image in a direction parallel to a thickness direction of each of the cell walls at a predetermined width.