A hydrogen generation system comprising: a reformer that produces a hydrogen-containing gas from a raw material and reforming water, the raw material and the reforming water being fed into the reformer; a combustor that burns the hydrogen-containing gas produced by the reformer and air, the air being fed into the combustor; an exhaust-gas path along which an exhaust gas generated from burning the hydrogen-containing gas and the air in the combustor flows; a cooling-water path along which cooling water is passed in order to cool the exhaust gas; a condenser that condenses moisture contained in the exhaust gas to produce condensed water by exchanging heat between the exhaust gas and the cooling water; a water tank that stores the condensed water, the condensed water serving as the cooling water; a water pump disposed downstream of the water tank in a direction in which the cooling water is passed along the cooling-water path, the water pump causing the cooling water stored in the water tank to be fed to the condenser; a reforming-water path branched from the cooling-water path at a junction formed at a portion of the cooling-water path between the water pump and the condenser, part of the cooling water being passed into the reformer along the reforming-water path, the part of the cooling water serving as the reforming water; and a controller, characterized in that the water tank being disposed at a position higher than the water pump, the water pump being disposed at a position higher than the junction, the water pump controlling the flow rate of the cooling water passed along the cooling-water path by changing the rotational speed of the water pump, the controller detecting that the amount of the cooling water stored in the water tank is equal to or less than a predetermined amount on the basis of the rotational speed of the water pump. a reformer that produces a hydrogen-containing gas from a raw material and reforming water, the raw material and the reforming water being fed into the reformer; a combustor that burns the hydrogen-containing gas produced by the reformer and air, the air being fed into the combustor; an exhaust-gas path along which an exhaust gas generated from burning the hydrogen-containing gas and the air in the combustor flows; a cooling-water path along which cooling water is passed in order to cool the exhaust gas; a condenser that condenses moisture contained in the exhaust gas to produce condensed water by exchanging heat between the exhaust gas and the cooling water; a water tank that stores the condensed water, the condensed water serving as the cooling water; a water pump disposed downstream of the water tank in a direction in which the cooling water is passed along the cooling-water path, the water pump causing the cooling water stored in the water tank to be fed to the condenser; a reforming-water path branched from the cooling-water path at a junction formed at a portion of the cooling-water path between the water pump and the condenser, part of the cooling water being passed into the reformer along the reforming-water path, the part of the cooling water serving as the reforming water; and a controller, characterized in that the water tank being disposed at a position higher than the water pump, the water pump being disposed at a position higher than the junction, the water pump controlling the flow rate of the cooling water passed along the cooling-water path by changing the rotational speed of the water pump, the controller detecting that the amount of the cooling water stored in the water tank is equal to or less than a predetermined amount on the basis of the rotational speed of the water pump.