A system according to one aspect of the present disclosure is a program updating system including a plurality of control devices installed in a vehicle, and a gateway capable of performing in-vehicle communication with the plurality of control devices. The gateway includes: a communication unit that receives a plurality of update programs for the control devices from an external device; a storage unit that stores therein the received plurality of update programs; an in-vehicle communication unit that transmits the stored plurality of update programs to the corresponding control devices, respectively; and a processing unit that prioritizes storage of a first program defined below into the storage unit over storage of a second program defined below into the storage unit.
First program: update programs of a plurality of control devices that require simultaneous updating
Second program: an update program of a control device that does not require simultaneous updating.