A device (1) for the manufacture of polyurethane foam with no bulky areas in the upper portion thereof, the invention being formed by a mould (2) and a base (3), the mould (2) having four lateral surfaces (4a, 4b, 4c, 4d) and a lower floating surface (5), the lateral surfaces (4a, 4b, 4c, 4d) forming the mould (2) upon being laterally attached by attaching means (7), and being separated in order to open the mould (2) and remove the polyurethane moulded piece, the lower floating surface (6) having a plurality of bars (8) arranged in a symmetric pattern, which are intended to generate corresponding orifices in the polyurethane moulded piece, also generating a uniform strength in said polyurethane moulded piece, where the lower surface (5) of the mould (2) is a floating surface, which may be lifted and lowered during the manufacturing process of the polyurethane foam. A process for manufacturing polyurethane moulded pieces is also included, the same comprising the use of the present devi ce (1) for the manufacture of said polyurethane foam, where the obtained moulded pieces have no bulky areas in the upper surface.Un dispositivo (1) para la fabricación de espuma de poliuretano que no presenta abultamiento en la parte superior que está formado por una porción de molde (2) y una porción de base (3), la porción de molde (2) presenta cuatro superficies (4a, 4b, 4c, 4d) laterales y una superficie inferior (5) flotante, las superficies (4a, 4b, 4c, 4d) laterales forman el molde (2) al estar unidas lateralmente mediante dispositivos (7) de unión que se pueden separar para permitir abrir el molde (2) y extraer de esta forma la pieza moldeada de poliuretano, la superficie inferior (6) flotante presenta una pluralidad de barras (8) dispuestas en un patrón simétrico, las cuales tienen como función generar orificios correspondientes en la pieza moldeada de poliuretano y al mismo tiempo generar una tensión uniforme en dicha pieza moldeada de poliuretano, en donde la superficie (5)
