This Study focuses on efficient management for a large-scale logistic center and proposes a new method how to assign stocked products to racks in a warehouse so as to minimize a round-up time (the maximum make-span time) to fetch ordered products. Self-organizing map (SOM), one of artificial neural networks, is employed to determine stocked products' allocation to the racks. In applying SOM, a number of order forms for rounding up the products are treated as a set of input signals and rack positions are regarded as SOM topology. Numerical simulation proves that the proposed method allow us to determine an efficient assignment of the stocked products to the racks.