Molding both faces of a honeycomb simultaneously by the action of respective belts carrying cores having resilience properties and, after cooling of the honeycomb, subjecting it to compression on both faces to separate the cores from the walls of the cells. The apparatus comprises two endless belts which are arranged opposite one another and are mounted between respective pairs of guide drums and both of which are provided with resilient cores of a shape complementary to that of the cells to be produced, the last pair of drums being capable of exerting a compression force against both faces of the honeycomb produced in order to detach it from the cores.