A USB device controller is applied to a peripheral device that performs data communications with a host by using a transmission endpoint and a reception endpoint via a USB interface. Herein, a USB endpoint controller performs data transmission and data reception by using the reduced number of memories, which contribute to downsizing of the circuit scale of the USB device controller. The USB endpoint controller contains a transmission control block, a reception control block and a buffer switch control block as well as the memories. The buffer switch control block controls allocation of the memories to a transmission endpoint and a reception endpoint respectively in response to a type of a token issued from the host. In response to an OUT token, the data transmission is performed on the transmission endpoint that actualizes a double buffer configuration while the reception endpoint is also available in data reception by a single buffer configuration. In response to an IN token, the data reception is performed on the reception endpoint that actualizes a double buffer configuration while the transmission endpoint is also available in data transmission by a single buffer configuration. Because of the actualization of the double buffer configuration, it is possible to perform high-speed processing in communications of data, particularly transaction data based on the updated standard of USB 2.0.