An exhaust gas processing device includes a honeycomb structure in a pillar shape including a honeycomb unit, a catalytic agent, an inorganic mat member, a cylindrical metallic member and an insulating layer. The honeycomb unit includes cell walls to define a plurality of cells which extend from a first end of the honeycomb unit to a second end of the honeycomb unit along a longitudinal direction. The catalytic agent is provided on the cell walls. The inorganic mat member is wound around an outer peripheral surface of the honeycomb structure. The cylindrical metallic member accommodates the honeycomb structure around which the inorganic mat member is wound. The insulating layer has a thickness of about 20 μm to about 400 μm and is densely formed. The insulating layer is provided between an inner surface of the cylindrical metallic member and the inorganic mat member.