A device for manufacturing three-dimensional objects using superimposed layers is capable, for each layer to be manufactured, of applying a laser beam treatment to a layer of a pulverulent material or liquid placed in a sintering field. The device includes a galvanometric head able to steer a laser beam toward each point of a maximum sintering zone of the sintering field when the galvanometric head is positioned at a predetermined position. The device further includes limiting elements for limiting the steering of the laser beam to an effective sintering zone situated inside the maximum sintering zone, and movement elements for moving the galvanometric head in a plane parallel to that of the sintering field, allowing the galvanometric head to be positioned at at least two different positions, an effective sintering zone being associated with each position of the galvanometric head. An associated method of manufacturing three-dimensional objects is described.