A fuel cell system includes a hydrogen gas supply portion for supplying a fuel cell with hydrogen gas. The hydrogen gas supply portion includes an odorant treatment portion for treating an odorant in a mixed gas containing given hydrogen gas and the odorant. The odorant treatment portion includes an odorant removal portion and an air blower. The odorant removal portion contains a porous adsorbent for adsorbing the odorant contained in the mixed gas and a catalyst for promoting decomposition of the adsorbed odorant. The air blower decomposes the adsorbed odorant. Thus, the odorant treatment portion can perform a function of supplying the fuel cell with hydrogen gas by adsorbing the odorant contained in the mixed gas, and a function of recovering its adsorption capacity by decomposing the adsorbed odorant.