A honeycomb structure comprising an outer peripheral wall; a partition wall defining a plurality of cells each extending from one end face to other end face, a plurality of slits extending radially inward from an outer peripheral surface of the honeycomb structure and extending in an extending direction of the cells; and a filling material filled in the slits. A difference between a width Y of the filling material when viewed from the outside in the radial direction of the honeycomb structure, and a width X of each of the slits on the outer peripheral surface of the honeycomb structure, represented by (Y−X), is determined for each of the slits, and a difference between a maximum value A of the difference and a minimum value B of the difference, represented by the (A−B), is 0.4 mm or less.