A device for machining a slot on a surface of a cellular structure includes a machining head that includes a chassis, a rotary tool rotating about a tool axis perpendicular to the direction of the slot, two guide wheels arranged on either side of the rotary tool that have a plurality of teeth configured and positioned such that they penetrate the cells of an alignment of the cellular structure. The machining head includes a link between the chassis and at least one guide wheel that enables a degree of freedom in a lateral direction parallel to the tool axis such that the guide wheel is movable in relation to the rotary tool in the lateral direction.