Working vehicle and attachment usage system

A working vehicle includes a first interface to receive input of first attachment information relating to an attachment attached to a hitch, a second interface to connect thereto at least one accessory electronic device provided in/on the attachment attached to the hitch, and a controller and a gateway which are connected to a bus. The gateway is connected to the second interface without the bus between the gateway and the second interface, and is configured or programmed to, if an external signal inputted thereto from the second interface does not agree with the attachment corresponding to the first attachment information, not output the external signal to the bus, and, if the external signal agrees with the attachment corresponding to the first attachment information, output the external signal to the bus. The controller is configured or programmed to perform control corresponding to the external signal inputted thereto via the bus.