To provide an automatic apparatus for opening and closing a fuel cap of a vehicle with which a fuel inlet door and the fuel cap can be opened or closed simultaneously and automatically.

This automatic fuel cap open/close apparatus comprises a first sensor 24 that is disposed to a cable 58 connected with an open lever 34 used for opening a fuel inlet door, and senses the operation of the open lever 34 when a power supply is turned on. This apparatus also includes a drive unit 26, an open/close member 28, and a second sensor 30. The drive unit 26 is applied with power supply through a first relay 44 and a transistor 50 when the first operation sensor 24 is energized, and is actuated to generate power. The open/close member 28 which opens and closes is installed by assembling with a fuel inlet 67 and interlocked with the driving unit 26. The second sensor 30 makes a second relay 68 and a transistor 72 applied with power supply when the open/close member 28 is inserted into the fuel inlet and actuates the driving unit.