An image processing system 1 (information processing system) includes a plurality of input interfaces 11, 12, and 13 for inputting image data output from a plurality of host systems C, PC1, and PC2, an input buffer 41 for storing the image data input through the input interfaces, determination mechanism for determining the upper limit value of the storage amount of the image data stored in the input buffer 41 for at least one of the input interfaces 11-13, and mechanism for storing image data in the input buffer in a scattering manner so as not to exceed the upper limit value determined by the determination mechanism.