A data transfer control device includes an OTG (state) controller which controls a plurality of states including a host operation state and a peripheral operation state, a host controller which is connected with a transceiver during the host operation, a peripheral controller which is connected with the transceiver during the peripheral operation, a register section including transfer condition registers which are used commonly during the host operation and the peripheral operation, and a buffer controller which controls access to a packet buffer used commonly by the host controller and the peripheral controller. Pipe regions PIPE0 to PIPEe are allocated in the packet buffer during the host operation, and endpoint regions EP0 to EPe are allocated in the packet buffer during the peripheral operation.