A sample analysis device comprising: a thermostatic chamber for holding a constant temperature fluid; a plurality of cells for containing a reaction solution; a cell disk for holding the plurality of cells being immersed in the constant temperature fluid inside the thermostatic chamber; a drive part adapted to rotationally drive the cell disk; a light emission unit for generating light to be radiated to the cells; a light receiving element for detecting the light having passed through the cells; and a holder placed inside the thermostatic chamber and holding the light emission unit and the light receiving element; characterized in that the holder includes a first vertical arm with a first flat surface, a second vertical arm with a second flat surface facing the first flat surface, and a connection arm connecting lower parts of the first vertical arm and the second vertical arm, wherein the first vertical arm includes the light emission unit and a light exit window provided on the first flat surface and the second vertical arm includes the light receiving element and a light entrance window provided on the second flat surface, such that the holder is adapted to hold the light emission unit and the light receiving element integrally with a constant distance between them and to be immersed with them in the constant temperature fluid such that both the light emission unit and the light receiving element as well as the constant temperature fluid between them can be kept at constant temperature inside the thermostatic chamber and such that, when one of the plurality of cells is positioned between the light exit window and the light entrance window, light emitted from the light emission unit can pass through the reaction solution in the cell to be received by the light receiving element; and the constant temperature fluid is water or oil. a thermostatic chamber for holding a constant temperature fluid; a plurality of cells for containing a reaction solution; a cell disk for holding the plurality of cells being immersed in the constant temperature fluid inside the thermostatic chamber; a drive part adapted to rotationally drive the cell disk; a light emission unit for generating light to be radiated to the cells; a light receiving element for detecting the light having passed through the cells; and a holder placed inside the thermostatic chamber and holding the light emission unit and the light receiving element; characterized in that the holder includes a first vertical arm with a first flat surface, a second vertical arm with a second flat surface facing the first flat surface, and a connection arm connecting lower parts of the first vertical arm and the second vertical arm, wherein the first vertical arm includes the light emission unit and a light exit window provided on the first flat surface and the second vertical arm includes the light receiving element and a light entrance window provided on the second flat surface, such that the holder is adapted to hold the light emission unit and the light receiving element integrally with a constant distance between them and to be immersed with them in the constant temperature fluid such that both the light emission unit and the light receiving element as well as the constant temperature fluid between them can be kept at constant temperature inside the thermostatic chamber and such that, when one of the plurality of cells is positioned between the light exit window and the light entrance window, light emitted from the light emission unit can pass through the reaction solution in the cell to be received by the light receiving element; and the constant temperature fluid is water or oil.