A vehicle information monitoring device for obtaining vehicle information from a vehicle control device that communicates with a vehicle information display device, the vehicle information display device being arranged so as to generate a request code directed to the vehicle control device and receive response data from the vehicle control device, the vehicle control device being arranged so as to generate response data including vehicle information according to a response code, characterized in that the vehicle information monitoring device comprises: first communication means (61, 51) for communicating with the vehicle information display device; second communication means (62, 52) for communicating with the vehicle control device; request control means (55, S1-S7) for causing the second communication means (62, 52) to transmit a second request code when the first communication means (61, 51) receives a first request code; response control means (55, S11-S17) for causing the first communication means (61, 51) to transmit response data corresponding to a first request code received by the first communication means (61, 51); and storage means for storing response data received by the second communication means (62, 52) in coordination with a second request code, wherein the request control means (55, S1-S7) is arranged so as to cause, if response data corresponding to the first request code is not stored in the storage means, the second communication means (62, 52) to transmit the first request code as the second request code, and cause, if response data corresponding to the first request code is stored in the storage means, the second communication means (62, 52) to transmit a third request code different from the first request code as the second request code, and the response control means (55, S11-S17) is arranged so as to cause the first communication means (61, 51) to transmit response data received by the second communication means (62, 52) when the second request code is equal to the first request code, and when the second request code is different from the first request code, read response data corresponding to the first request code out of the storage means and cause the first communication means (61, 51) to transmit the response data. the vehicle information display device being arranged so as to generate a request code directed to the vehicle control device and receive response data from the vehicle control device, the vehicle control device being arranged so as to generate response data including vehicle information according to a response code, characterized in that the vehicle information monitoring device comprises: first communication means (61, 51) for communicating with the vehicle information display device; second communication means (62, 52) for communicating with the vehicle control device; request control means (55, S1-S7) for causing the second communication means (62, 52) to transmit a second request code when the first communication means (61, 51) receives a first request code; response control means (55, S11-S17) for causing the first communication means (61, 51) to transmit response data corresponding to a first request code received by the first communication means (61, 51); and storage means for storing response data received by the second communication means (62, 52) in coordination with a second request code, wherein first communication means (61, 51) for communicating with the vehicle information display device; second communication means (62, 52) for communicating with the vehicle control device; request control means (55, S1-S7) for causing the second communication means (62, 52) to transmit a second request code when the first communication means (61, 51) receives a first request code; response control means (55, S11-S17) for causing the first communication means (61, 51) to transmit response data corresponding to a first request code received by the first communication means (61, 51); and storage means for storing response data received by the second communication means (62, 52) in coordination with a second request code, wherein the request control means (55, S1-S7) is arranged so as to cause, if response data corresponding to the first request code is not stored in the storage means, the second communication means (62, 52) to transmit the first request code as the second request code, and cause, if response data corresponding to the first request code is stored in the storage means, the second communication means (62, 52) to transmit a third request code different from the first request code as the second request code, and the response control means (55, S11-S17) is arranged so as to cause the first communication means (61, 51) to transmit response data received by the second communication means (62, 52) when the second request code is equal to the first request code, and when the second request code is different from the first request code, read response data corresponding to the first request code out of the storage means and cause the first communication means (61, 51) to transmit the response data.