A fuel tank opening-closing device includes a shutter mechanism situated inside a tank neck defining member and adapted to open a shutter body in response to insertion of a fuel nozzle. The shutter mechanism includes a push mechanism having a push member situated in an insertion passage; an interconnection mechanism having springs adapted to accumulate force of displacement of the push member as mechanical energy; and a nozzle sensing mechanism. The nozzle sensing mechanism has introduction pressure members adapted to receive displacement force of the fuel nozzle in the insertion direction, and lock portions that allow the shutter to move to the opening position.