A program update system includes a vehicle including a plurality of in-vehicle devices, and a server provided outside the vehicle. Each of the in-vehicle devices of the vehicle includes a storage unit configured to store one or more programs, an in-vehicle device communication unit configured to perform communication with the server, and an update execution unit configured to update the programs stored in the storage unit. The server includes a server communication unit configured to perform communication with each of the in-vehicle devices, and an update management unit configured to specify the in-vehicle device to be updated in a set of the in-vehicle devices and a program to be updated and execute update processing that makes the server communication unit transmit update data for updating the program to be updated to the in-vehicle device to be updated.