The fuel cell system includes: a power generation unit; an obtaining unit obtaining battery information indicating a storage state of a storage battery; and a control unit selecting one of a first control mode and a second control mode based on the battery information when load power changes from a first load power to a second load power, the first control mode being for supplying power from the power generation unit to the load by causing the power generation unit to generate power without causing the storage battery to charge and/or discharge, the second control mode being for causing the power generation unit to generate power with a change rate of generation power being set to a value smaller than a value in the first control mode, by causing the storage battery to charge and/or discharge.