The manufacturing method of the present invention is to manufacture a fuel cell stack by heating a stack of fuel cell single cells each of which includes organic substance-containing inorganic sealing members, a separator, an anode electrode, an electrolyte and a cathode electrode. The organic substance in the organic substance-containing inorganic sealing members is removed by heating the stack while supplying an oxygen-containing gas to fuel channels on the anode electrode side and externally applying an electric current so as to migrate charges from the anode electrode to the cathode electrode.