A fuel cell system comprising: a hydrogen tank to store hydrogen, the hydrogen tank including a hydrogen storage alloy; and a fuel cell to receive hydrogen gas from the hydrogen tank to generate electricity, characterized by comprising: a temperature controller to adjust a temperature inside the hydrogen tank; and a control unit to control the temperature controller based on the amount of hydrogen remaining in the hydrogen tank, the control unit being configured to increase the temperature inside the hydrogen tank when the amount of the remaining hydrogen is equal to or less than a first predetermined value; and a first circulating water supply passage for circulation of first circulating water to adjust the temperature inside the hydrogen tank, wherein the temperature controller includes a heater to increase a temperature of the first circulating water, the first circulating water supply passage being provided with the heater, and the control unit is configured to, when the amount of the remaining hydrogen is equal to or less than the first predetermined value, start energizing the heater to increase the temperature inside the hydrogen tank, calculate a target temperature from the calculated amount of the remaining hydrogen based on a characteristics map of temperature versus the amount of the remaining hydrogen, and control the heater to control an actual temperature of the first circulating water flowing in the first circulating water supply passage at the target temperature thus calculated. a hydrogen tank to store hydrogen, the hydrogen tank including a hydrogen storage alloy; and a fuel cell to receive hydrogen gas from the hydrogen tank to generate electricity, characterized by comprising: a temperature controller to adjust a temperature inside the hydrogen tank; and a control unit to control the temperature controller based on the amount of hydrogen remaining in the hydrogen tank, the control unit being configured to increase the temperature inside the hydrogen tank when the amount of the remaining hydrogen is equal to or less than a first predetermined value; and a temperature controller to adjust a temperature inside the hydrogen tank; and a control unit to control the temperature controller based on the amount of hydrogen remaining in the hydrogen tank, the control unit being configured to increase the temperature inside the hydrogen tank when the amount of the remaining hydrogen is equal to or less than a first predetermined value; and the temperature controller includes a heater to increase a temperature of the first circulating water, the first circulating water supply passage being provided with the heater, and the control unit is configured to, when the amount of the remaining hydrogen is equal to or less than the first predetermined value, start energizing the heater to increase the temperature inside the hydrogen tank, calculate a target temperature from the calculated amount of the remaining hydrogen based on a characteristics map of temperature versus the amount of the remaining hydrogen, and control the heater to control an actual temperature of the first circulating water flowing in the first circulating water supply passage at the target temperature thus calculated.