A method for manufacturing an exhaust gas treatment device (1), which has at least one ceramic substrate body (3, 4) for exhaust gas treatment in a tubular housing (2), includes inserting the substrate body (3) axially into the housing (2). An axial support (13), which has a supporting ring (14) and a ring-shaped support element (15) held by the supporting ring (14), is inserted axially into the housing (2) and is positioned therein such that the axial support (13) transmits a predetermined axial force (28) to the substrate body (3) via the support element (15). The axial support (13) is fixed to the housing (2) with the axially prestressed (predetermined axial force) positioning, in which the supporting ring (14) is welded to the housing (2).