A gas-removing device serves to remove impurity gases from the air supplied to a fuel cell via an air supply system. The gas-removing device includes a porous material and an alternate adsorption membrane. The porous material has micropores formed therein in order to absorb impurity gas particles contained in the air. The alternate adsorption membrane is formed on the inner walls of the micropores of the porous material in order to further adsorb and retain at least one type of impurity gas particles from among the impurity gas particles absorbed by the porous material. The alternate adsorption membrane includes at least one positively charged layer and at least one negatively charged layer laid alternately to one another.