Abstract: A liquid fuel storage device is provided for use with an automobile system including an engine, a fuel tank, and a canister for absorbing fuel vapor during refueling. The device includes an air bag disposed in the fuel tank and constructed and arranged to inflate to occupy a space in the fuel tank in accordance with an amount fuel remaining in the fuel tank. Piping structure communicates the fuel tank with the engine for inflating the air bag by reducing pressure in the fuel tank when the engine is started. An air introduction pipe communicates with the atmosphere and includes a first valve mechanism for introducing air into the air bag and prevents air from escaping from the air bag after inflation thereof. An air emission pipe includes a second valve mechanism, which is opened only in refueling to emit air in the air bag during refueling. The air emission pipe is connected to the canister.