Fuel cell device

A fuel cell device comprising:

• a cell stack including a plurality of unit cells that are stacked;
• a case including a cover portion that covers one of side surfaces of the cell stack, the side surfaces of the cell stack extending along a stacking direction along which the plurality of unit cells are stacked;
• an end plate connected to one end portion of the cover portion in the stacking direction and disposed on an outer side of the cell stack in the stacking direction;
• and
• a fastening member that extends in parallel with the stacking direction on an opposite side of the cell stack from the cover portion, that includes one end portion in the stacking direction connected to the end plate and another end portion in the stacking direction connected to the case, and that fastens the cell stack, the end plate, and the case to each other and compresses the cell stack, the end plate, and the case in the stacking direction, wherein
• a thermal expansion coefficient of the cover portion is larger than a thermal expansion coefficient of the fastening member, and
• a rigidity of the fastening member is lower than a rigidity of the cover portion.