To provide a fuel cell system capable of determining that replacement parts are normally mounted after the replacement.

The system includes a fuel cell 1 having an anode electrode 10 and a cathode electrode 11, the replaceable parts having a function contributing to power generating operation of the fuel cell 1, and an element to utilize at least one function out of the functions which the replacement parts have. An operation part 2 is arranged which operates power generation of the fuel cell 1 by supplying an anode fluid to the anode electrode 10 and a cathode fluid to the cathode electrode 11. A control device 8 carries out acquisition operation to acquire a state of an element out of the operation part 2, and replacement appropriateness determination operation to output an alarm when the state of the acquired element does not have a state of the element when the replacement parts are normally operated.