A control device comprises an acquisition unit that acquires a current to or from the battery and a voltage of a battery, a calculation unit that calculates an internal resistance of the battery based on the current and the voltage when the regenerative power generation is performed by a rotary electric machine, and a permission determination unit that determines whether to permit an automatic stop of an engine depending on whether restarting of the engine is enabled based on power running drive of the rotary electric machine. The calculation unit calculates a value of the internal resistance each time the regenerative power generation or the power running drive is performed before the engine enters an automatic stop state. The permission determination unit determines whether to permit the automatic stop based on a latest value of the internal resistance among values of the internal resistance calculated by the calculation unit.