A fuel cell apparatus, comprising: a reformer for generating an anode gas including hydrogen by reforming a fuel gas by means of water vapor generated at an evaporating portion, the reformer being arranged to extend in a lengthwise direction thereof; a combusting portion forming a combusting space in which combustion flame heating the reformer is generated; a stack supplied with the anode gas and a cathode gas to generate electric power; a heat insulating wall surrounding the reformer and the stack; and a fixing portion arranged along the heat insulating wall, wherein a first end portion of the reformer in the lengthwise direction thereof is fixed to a part of the fixing portion at a welded portion (701, 702, 704, 705) or by means of a fixture so that a displacement of the first end portion which occurs in association with a thermal expansion of the reformer in the lengthwise direction is restrained, characterized in that a second end portion of the reformer in the lengthwise direction thereof is placed at a placement surface (802, 802E, 802F) of the heat insulating wall in a manner that the second end portion is relatively displaceable in the lengthwise direction of the reformer in association with the thermal expansion, the heat insulating wall faces, in a horizontal direction perpendicular to the lengthwise direction of the reformer, a side surface of the second end portion of the reformer in the lengthwise direction thereof and the heat insulating wall includes a lateral-facing restraining surface for restraining the side surface of the second end portion in the horizontal direction, and a first clearance is provided between the side surface of the second end portion of the reformer and the lateral-facing restraining surface of the heat insulating wall in the horizontal direction, and the first clearance is configured to absorb a displacement of the second end portion of the reformer in the horizontal direction. a reformer for generating an anode gas including hydrogen by reforming a fuel gas by means of water vapor generated at an evaporating portion, the reformer being arranged to extend in a lengthwise direction thereof; a combusting portion forming a combusting space in which combustion flame heating the reformer is generated; a stack supplied with the anode gas and a cathode gas to generate electric power; a heat insulating wall surrounding the reformer and the stack; and a fixing portion arranged along the heat insulating wall, wherein a first end portion of the reformer in the lengthwise direction thereof is fixed to a part of the fixing portion at a welded portion (701, 702, 704, 705) or by means of a fixture so that a displacement of the first end portion which occurs in association with a thermal expansion of the reformer in the lengthwise direction is restrained, characterized in that a second end portion of the reformer in the lengthwise direction thereof is placed at a placement surface (802, 802E, 802F) of the heat insulating wall in a manner that the second end portion is relatively displaceable in the lengthwise direction of the reformer in association with the thermal expansion, the heat insulating wall faces, in a horizontal direction perpendicular to the lengthwise direction of the reformer, a side surface of the second end portion of the reformer in the lengthwise direction thereof and the heat insulating wall includes a lateral-facing restraining surface for restraining the side surface of the second end portion in the horizontal direction, and a first clearance is provided between the side surface of the second end portion of the reformer and the lateral-facing restraining surface of the heat insulating wall in the horizontal direction, and the first clearance is configured to absorb a displacement of the second end portion of the reformer in the horizontal direction.