A method for automatically cutting off power in case of a low battery voltage in a mobile electronic unit is provided. The method comprises (a) cutting off the power of the mobile electronic unit when a battery voltage is detected in a first check section during a booting period of the mobile electronic unit that is not in a normal state, and (b) cutting off the power of the mobile electronic unit when the battery voltage detected with respect to the first check section is in the normal state and when a battery voltage is detected in a second check section during a period after booting of the mobile electronic unit is completed that is not in the normal state.