A treatment device for transport and storage boxes according to the invention comprises a plurality of decontamination modules (24-27) supported by a common chassis (100) and arranged in a row of at least one column (23c) of modules superposed one on top of the other. Each decontamination module (24-27) comprises its own pumping means (6) having at least a primary pump (8a) housed in a primary pumping compartment (8c) that is longitudinally offset from the decontamination chamber (5). Access to the decontamination modules (24-27) is had via side access doors which are all oriented on one and the same access side and which are acted upon by actuating means that automatically close and open them. A lateral transfer zone is provided on the access side, and comprises a robot (29) capable of moving the transport and storage boxes between a frontal loading-unloading station (23a) and the decontamination chambers (5) of each of the decontamination modules (24-27). The amount of space occupied by and the throughput of the treatment device (23) are thus optimized.