An apparatus is configured to make containers from sheet material. The apparatus includes a supply station for supplying a film having at least one folded portion having three or more film flaps folded and superimposed with respect to each other; a welding station configured to receive the film. The welding station comprises a welding head configured for welding the folded portion of the film and forming a container defining a housing compartment; the welding head comprises a heater made of electrically conductive material whose electrical resistivity, at least in a predetermined temperature range, decreases upon the increase of the temperature of the same electrically conductive material.