A heater for heating a reformer of a fuel cell system includes a combustion chamber having a combustion catalyst layer; a distributor having an inner space and uniformly distributing a combustion fuel and an oxidant flowing along the inner space to the combustion catalyst layer of the combustion chamber; and an igniter igniting the combustion fuel and the oxidant, wherein the igniter is placed in the inner space of the distributor. Thus, the igniter is protected from combustion heat of the combustion catalyst layer and thus has improved durability.