An endless conveyor belt for a conveyor device, includes a planar body (2) that is transversely deformable into a tubular configuration, the body having a plurality of longitudinal reinforcing members built into the body thereof. The body has an upper layer (10), a portion of the lower surface of which is combined with a lower layer (11). The two layers are made of two different elastomer materials, with the lower layer made of a first elastomer material, whose hardness is greater than that of the second elastomer material constituting the upper layer, and the lower layer includes a plurality of softening recesses (13) that are distributed across the entire length of the lower layer and each of which extend over at least a portion of the body thereof so as to reduce the resistance thereof to longitudinal deformations in order to reduce the resistance to the bending of the conveyor belt into the tubular configuration thereof.