RELAY DEVICE, PROGRAM, AND METHOD FOR UPDATING PROGRAM

A relay device for obtaining an update program transmitted from a vehicle-outside device and performing processing for updating a program of an in-vehicle ECU mounted in a vehicle, the relay device including: a control unit for performing relay processing with the in-vehicle ECU; and a storage unit having stored thereon a relay processing program used for relay processing and a switch program for switching between relay processing and update processing; in which the control unit: obtains an update processing program for performing update processing from the vehicle-outside device; stores the obtained update processing program in the storage unit by using a storage area where the relay processing program is stored; and executes the update processing program stored in the storage unit; and while executing the update processing program, the control unit outputs the update program obtained from the vehicle-outside device to the in-vehicle ECU to be updated.