A program update method includes a first step of acquiring a remaining capacity of electric power stored in an electric power storage device, a second step of acquiring an electric power amount required for the control device to update the control program, a third step of determining whether the remaining capacity is smaller than the electric power amount, a fourth step of charging the electric power storage device such that the remaining capacity becomes the electric power amount or larger when it is determined that the remaining capacity is smaller than the electric power amount in the third step, and a fifth step of causing the control device to update the control program when the remaining capacity becomes the electric power amount or larger in the fourth step. The first to fifth steps are performed when the vehicle is operating.