The invention relates to a conveyor device consisting of: at least one base module (1) having a central structure comprising opposing C-shaped sides (10), the bends in which comprise runners (31, 32) which are used to support and guide the upper and lower lines of the belt, said sides (10) forming a closed case with the belt; and end modules (2) which are arranged to receive and support each end of a base module (1) and which comprise a motorised or non-motorised belt-winding pulley. Depending on the case, the conveyor device comprises an intermediary module (3) which essentially corresponds to the assembly of two end modules (2) positioned back to back and which is disposed between the ends of two base modules (1). The device also comprises auxiliary belt-type (6a) conveyor means (7) which provide a continuous conveying surface between the belts (6) of the base modules (1).