A buffer is provided with a CBW area (a randomly accessible command storage area) and an EP1 area (data storage area set to FIFO), when a CBW and data are allocated as informations to be transferred through one end point EP1. When a phase switches from a USB command phase (command transport) to a data phase (data transport), the information write area is switched from the CBW area to the EP1 area and OUT data transferred from the host to the end point EP1 is written into the EP1 area. The area switches from the CBW area to the EP1 area on condition that an acknowledgment has returned to the host in the command phase. In case of a toggle missing, area switching does not occur even if ACK is returned.