Method for manufacturing a cushion of a motor vehicle seat, said method comprising the following steps: - providing a shaping device comprising, on the one hand, a die provided with orifices connected to a vacuum circulation device and, on the other hand, a heating punch, - providing a reaction injection mould, said mould comprising a vessel and a lid defining a mould cavity, - disposing a cover made of a flexible coating in said die, the viewing face of said cover facing said die, - covering said cover with a thermoplastic polyurethane-based bonding film with a melting point of between 100 and 110°C, - producing a peripheral seal by means of a blank holder bearing against the periphery of said cover, - actuating said vacuum circulation device so that said film presses said cover against said die to mould to the geometry thereof, - disposing a support layer made of flexible foam on said film, said layer being equipped with at least one functional element so as to form an equipped layer, - pressing said equipped layer against said film by means of said punch heated to a temperature that allows said film to melt to obtain adhesion between said cover and said equipped layer, - disposing said cover provided with said equipped layer in said vessel and covering said layer with a protective film arranged so as to degrade under the effect of the temperature and pressure involved during the expansion of a resiliently-compressible polyurethane foam, - injecting a precursor mixture of resiliently-compressible polyurethane foam into said cavity on said protective film so as to form, after said foam has expanded and said protective film has degraded, a block of padding overmoulding said cover provided with said equipped layer, - removing the cushion obtained from the mould. - providing a shaping device comprising, on the one hand, a die provided with orifices connected to a vacuum circulation device and, on the other hand, a heating punch, - providing a reaction injection mould, said mould comprising a vessel and a lid defining a mould cavity, - disposing a cover made of a flexible coating in said die, the viewing face of said cover facing said die, - covering said cover with a thermoplastic polyurethane-based bonding film with a melting point of between 100 and 110°C, - producing a peripheral seal by means of a blank holder bearing against the periphery of said cover, - actuating said vacuum circulation device so that said film presses said cover against said die to mould to the geometry thereof, - disposing a support layer made of flexible foam on said film, said layer being equipped with at least one functional element so as to form an equipped layer, - pressing said equipped layer against said film by means of said punch heated to a temperature that allows said film to melt to obtain adhesion between said cover and said equipped layer, - disposing said cover provided with said equipped layer in said vessel and covering said layer with a protective film arranged so as to degrade under the effect of the temperature and pressure involved during the expansion of a resiliently-compressible polyurethane foam, - injecting a precursor mixture of resiliently-compressible polyurethane foam into said cavity on said protective film so as to form, after said foam has expanded and said protective film has degraded, a block of padding overmoulding said cover provided with said equipped layer, - removing the cushion obtained from the mould.