A power supply control apparatus of a navigation system includes a power switch for a user to turn a display screen of the navigation system on or off; a navigation power switching unit to turn an internal function of the navigation system on or off by a power supply connection; a navigation information unnecessary state detecting unit to detect a navigation information unnecessary state where a user does not need navigation information; and a power supply control unit to turn the navigation power switching unit off when the navigation information unnecessary state detecting unit detects the navigation information unnecessary state.