FUEL CELL SYSTEM

A fuel cell system for generating power by supplying a reaction gas to a fuel cell includes a wet state detection unit configured to detect a wet state of an electrolyte membrane of the fuel cell, a steady time target wet state setting unit configured to set a steady time target wet state of the electrolyte membrane during a steady operation of the fuel cell system based on an operating condition of the fuel cell system, and a transient time target wet state setting unit configured to set a transient time target wet state so that the wet state of the electrolyte membrane gradually changes from a wet state detected before a transient operation starts to the steady time target wet state during the transient operation in which the operating condition of the fuel cell system changes.