An erroneous fuel feed prevention device includes paired flaps having a surface slanted relative to a direction of insertion of a fuel feeding nozzle. A turn shaft part, a support hole, and paired extension portions are provided. A first biasing member is configured to bias flaps of the paired extension portions to turn in a closing direction. A first restriction portion and a second restriction portion are configured to restrict the flaps from turning in an opening direction. While slanted surfaces are pressed by the fuel feeding nozzle, each of the flaps slide outward in radial directions of the fuel feed passage to release turning restriction states of the first restriction portion and the second restriction portion, and after the release, the flaps turn in an integrated manner with the extension portions being in contact with the respective other flaps.