A fuel cell power system includes a fuel cell stack prepared by stacking a plurality of electric cells, each having an anode and a cathode with an electrolyte therebetween, a fuel supply line and an oxidant supply line that respectively supply a fuel and an oxidant to the fuel cell stack, and a fuel exhaust line and an oxidant exhaust line that respectively exhaust the fuel and oxidant supplied to the fuel cell stack. A method for retaining a power generation-suspended state of the fuel cell power system in a process of bringing the fuel cell power system into the power generation-suspended state and retaining the suspended state includes the steps of: closing the oxidant supply line in the course of bringing the fuel cell power system into the power generation-suspended state; applying a direct current from the cathode to the anode through an external circuit with the oxidant supply line closed by the step of closing the oxidant supply line until the electric cell voltage with reference to the anode comes to a level of more than −1.2 V to less than 0.1 V; closing the oxidant exhaust line after the start point of the step of applying a direct current; and closing the fuel exhaust line and the fuel supply line after the termination point of the step of applying a direct current.