The present invention provides an outer layer fixing mechanism used for an analysis device, which can fix the outer-layer parts mutually with simple work and can be manufactured by a low-cost manufacturing cost. An elastic body comprising a groove is arranged in a first outer-layer part, and a plate-like part comprising a concave part is arranged in a second outer-layer part. From a state that thefirst outer-layer part and the second outer-layer part are opposite, and after the first outer-layer part and the second outer-layer part move in a approaching manner, the peripheral part of the concave part of the plate-like part is embedded in the groove of the elastic body, and the first outer-layer part and the second outer-layer part are fixed, so that the first outer-layer part and the second outer-layer part can be fixed with simple work, and the simple work represents that the first outer-layer part and the second outer-layer part move in the approaching manner, and the elastic body is inserted in the concave part of the plate-like part. In addition, the plate-like part is manufactured by the blow molding.