A vehicle electronic control system includes a center device and a vehicle master device. The center device includes: a campaign information obtainer obtaining campaign information of a program update; a vehicle state obtainer obtaining a vehicle state of a target vehicle of the program update; an execution requirement setter setting an execution requirement of a phase in the program update based on the campaign information obtained by the campaign information obtainer and the vehicle state obtained by the vehicle information obtainer; an execution requirement notifier notifying the vehicle master device of the execution requirement set by the execution requirement setter; and an update data deliverer delivering the update data to the vehicle master device.