A warehousing system includes a multistory building having at least one lower floor, at least one upper floor located above the lower floor, opposed pairs of rack members disposed on the upper floor, and an aisle formed between each of the pairs of the rack members. Each pair of the rack members has two opposed horizontal guide rails respectively formed thereon at two sides of the aisle. A hole is formed in the upper floor at the aisle to intercommunicate respectively with the lower floor. A conveying device is disposed movably on the horizontal guide rails. The conveying device includes a translation device having a base bridging the aisle and connected slidably to the horizontal guide rails, a driving device disposed on the base for driving the base to move along the horizontal guide rails in a first direction, a holding apparatus mounted on the base and adapted for holding an article to be conveyed, and an elevator apparatus disposed on the base for raising and lowering the holding apparatus from the base. The elevator apparatus is movable relative to the base to lower the holding apparatus through the hole into the lower floor.