An exhaust gas cleaning device is constructed of a honeycomb core body. The honeycomb core body has been formed by superposing a planar band made of a metal sheet and a corrugated band made from another metal sheet one over the other in a contiguous relationship and then rolling the thus-superposed bands into a multi-layered spiral form. The honeycomb core body defines a number of network-patterned axial gas flow passages and is adapted to carry an exhaust gas cleaning catalyst. The honeycomb core body is divided into a central honeycomb core section of a smaller diameter and an outer honeycomb core section of a larger diameter. A separator is interposed between an outer peripheral wall of the central honeycomb core section and an inner peripheral wall of the outer honeycomb core section. The outer honeycomb core section may be divided further into plural honeycomb core sub-sections having different diameters and a additional separator may be interposed between each two adjacent core sub-sections.