A gateway device connected to a bus of a first network through which a frame of a first type is transmitted using the bus in accordance with a first communication protocol, which is a CAN, Controller Area Network, protocol, and a second network through which a frame of a second type is transmitted in accordance with a second communication protocol, which is an Ethernet protocol and which is different from the first communication protocol, wherein the first and second networks are vehicle networks and wherein the gateway device is connected to an Ethernet cable included in the second network, the gateway device comprising: a reception unit that sequentially receives the frame of the first type from the bus, wherein the frame of the first type is a data frame including a CAN-ID and, in a data field, the data; and a determination unit that determines whether to transmit data regarding the frame of the first type received by the reception unit to the second network; and determines, on the basis of the CAN-ID of the frame of the first type received by the reception unit, whether to transmit the data regarding the frame of the first type to the second network, and also refers to the reference information in which the plurality of destinations and the CAN-IDs are associated with each other and selects, on the basis of the CAN-ID of the frame of the first type received by the reception unit, one of the plurality of destinations as a destination of the data regarding the frame of the first type to be transmitted to the second network; and a transmission unit that transmits, to the second network, the frame of the second type including data regarding a plurality of frames of the first type determined by the determination unit to be transmitted to the second network by outputting the frame of the second type to the cable, wherein the frame of the second type is an Ethernet frame including an Ethernet header and a payload, and transmits the frame of the second type including the data regarding the plurality of frames of the first type determined by the determination unit to be transmitted to the second network and destination information indicating the destination of the data selected by the determination unit in the payload. a reception unit that sequentially receives the frame of the first type from the bus, wherein the frame of the first type is a data frame including a CAN-ID and, in a data field, the data; and sequentially receives the frame of the first type from the bus, wherein the frame of the first type is a data frame including a CAN-ID and, in a data field, the data; and a determination unit that determines whether to transmit data regarding the frame of the first type received by the reception unit to the second network; and determines, on the basis of the CAN-ID of the frame of the first type received by the reception unit, whether to transmit the data regarding the frame of the first type to the second network, and also refers to the reference information in which the plurality of destinations and the CAN-IDs are associated with each other and selects, on the basis of the CAN-ID of the frame of the first type received by the reception unit, one of the plurality of destinations as a destination of the data regarding the frame of the first type to be transmitted to the second network; and determines whether to transmit data regarding the frame of the first type received by the reception unit to the second network; and determines, on the basis of the CAN-ID of the frame of the first type received by the reception unit, whether to transmit the data regarding the frame of the first type to the second network, and also refers to the reference information in which the plurality of destinations and the CAN-IDs are associated with each other and selects, on the basis of the CAN-ID of the frame of the first type received by the reception unit, one of the plurality of destinations as a destination of the data regarding the frame of the first type to be transmitted to the second network; and a transmission unit that transmits, to the second network, the frame of the second type including data regarding a plurality of frames of the first type determined by the determination unit to be transmitted to the second network by outputting the frame of the second type to the cable, wherein the frame of the second type is an Ethernet frame including an Ethernet header and a payload, and transmits the frame of the second type including the data regarding the plurality of frames of the first type determined by the determination unit to be transmitted to the second network and destination information indicating the destination of the data selected by the determination unit in the payload. transmits, to the second network, the frame of the second type including data regarding a plurality of frames of the first type determined by the determination unit to be transmitted to the second network by outputting the frame of the second type to the cable, wherein the frame of the second type is an Ethernet frame including an Ethernet header and a payload, and transmits the frame of the second type including the data regarding the plurality of frames of the first type determined by the determination unit to be transmitted to the second network and destination information indicating the destination of the data selected by the determination unit in the payload.