There have been insufficient highly reliable responses appropriate to the causes of power generation abnormalities in fuel cells that generate power by supplying an oxidizing agent containing oxygen to the cathode and by supplying a fuel gas containing hydrogen to the anode. In order to overcome this problem the invention provides for a fuel cell power generation system equipped with a means that includes AC signal generation block 503 and load 502 that varies the load current for fuel cell 501, which operates to generate power; voltage measurement block 504 that measures the voltage response to the load current variation; impedance measurement block 505 that computes the impedance of fuel cell 501, based on the results of the measurement of the voltage response; and fuel cell control block 506 that varies the operating conditions of fuel cell 501, by utilizing the impedance computation results.