1. A USB host system for performing USB data transfer with a USB device connected thereto, the system comprising: a USB host controller which is compliant with an OHCI standard and includes a transfer memory for USB data transfer; a memory; a data transfer processing block for performing internal data transfer between the memory and the transfer memory; and transfer descriptor setting means for setting, for the USB host controller, a transfer descriptor for executing USB data transfer, wherein in the transfer memory, first through Nth (N is an integer of 2 or larger) transfer descriptor regions are allocated, and wherein the transfer descriptor setting means is configured so as to be able to set, for one end point of the USB device, a plurality of transfer descriptors using the first through Nth transfer descriptor regions, respectively.