A gas vapor control system may include a canister for capturing gas vapor that is generated from a fuel, a throttle valve that is disposed substantially in the middle of an intake passage through which air flows into a cylinder of the engine, a gas passage that communicates from the canister to one side downstream of the throttle valve, a purge control valve that is disposed on the gas passage, and a control portion that stops an engine in an idle state and controls a real fuel injection amount that is to be injected while restarting the engine according to a first fuel amount that is included in gas vapor that is discharged into the intake passage.