Program update method, program update system and mobile object

A mobile object comprises an acquisition processor acquiring new program from an external apparatus via a network; a rewriting control processor performing a rewriting control of rewriting a program of an electronic control unit equipped with the mobile object, the rewriting being performed by using the acquired new program when driving operation of the mobile object is disabled; a storage compartment covered by a hood; a hood latch; and a battery stored in the storage compartment and configured to supply electrical power to the rewriting control processor and the electronic control unit. The rewriting control processor locks the hood latch such that the hood may not be opened when performing the rewriting control of rewriting the program of the electronic control unit.