A honeycomb structure includes at least one pillar-shaped honeycomb unit and a pair of electrodes. The pillar-shaped honeycomb unit includes an outer peripheral wall and cell walls. The cell walls extend along a longitudinal direction of the honeycomb unit to define cells. The cell walls are composed of a ceramic aggregate having pores. The cell walls contain a substance having an electrical resistivity lower than an electrical resistivity of ceramic forming the ceramic aggregate. The pair of electrodes is arranged at the cell walls and/or the outer peripheral wall.