When a first automatic stopping condition is established while a vehicle (1A, 1B) is stationary or a second automatic stopping condition is established during travel, an internal combustion engine (2) of the vehicle is automatically stopped. The first automatic stopping condition is established when a battery voltage or a battery state of charge of a battery (21) equals or exceeds a first threshold, and the second automatic stopping condition is established when the battery voltage or the battery state of charge of the battery (21) equals or exceeds a second threshold. By setting the second threshold to be greater than the first threshold, opportunities for automatically stopping the internal combustion engine (2) are secured while satisfying a power requirement of an electrical load (26, 27) during restarting of the internal combustion engine (2).