A data processing apparatus includes multiple processing means that are connected in a ring shape via corresponding communication means respectively. Each communication means includes a reception means for receiving data from a previous communication means, and a transmission means for transmitting data to a next communication means. Connection information is assigned to each of the reception means and the transmission means. The communication means, when receiving a packet that has same connection information as one assigned to its reception means, causes the corresponding processing means to perform data processing on the packet, sets the connection information assigned to its transmission means to the packet, and transmits the packet to the next communication means, and when receiving a packet that has connection information that is not same as one assigned to its reception means, transmits the packet to the next communication means without changing the connection information of the packet.