A spectrometer comprising: a package having a stem and a cap provided with a light entrance part; an optical unit arranged on the stem within the package; and wherein the optical unit has: a dispersive part for dispersing and reflecting light entering the package from the light entrance part; a light detection element for detecting the light dispersed and reflected by the dispersive part; a support for supporting the light detection element, such as to form a space between the dispersive part and the light detection element, characterized in that the support is a hollow structure that includes a base wall part, arranged so as to oppose the stem, having the light detection element secured thereto, and a side wall part, arranged so as to erect from a side of the dispersive part to the stem, for supporting the base wall part, and in that the spectrometer further comprises a lead pin penetrating through the stem, a projection projecting from the support, wherein the base wall part, side wall part, and projection are formed integrally; and a wiring including a first terminal part electrically connected to a terminal of the light detection element and a second terminal part arranged in the projection; wherein the projection is arranged at such a position as to be separated from the stem and to project from the side wall part to the side opposite from the dispersive part; and wherein the lead pin is electrically connected to the second terminal part while being disposed to the projection. a package having a stem and a cap provided with a light entrance part; an optical unit arranged on the stem within the package; and wherein the optical unit has: a dispersive part for dispersing and reflecting light entering the package from the light entrance part; a light detection element for detecting the light dispersed and reflected by the dispersive part; a support for supporting the light detection element, such as to form a space between the dispersive part and the light detection element, characterized in that the support is a hollow structure that includes a base wall part, arranged so as to oppose the stem, having the light detection element secured thereto, and a side wall part, arranged so as to erect from a side of the dispersive part to the stem, for supporting the base wall part, and in that the spectrometer further comprises a lead pin penetrating through the stem, a projection projecting from the support, wherein the base wall part, side wall part, and projection are formed integrally; and a wiring including a first terminal part electrically connected to a terminal of the light detection element and a second terminal part arranged in the projection; wherein the projection is arranged at such a position as to be separated from the stem and to project from the side wall part to the side opposite from the dispersive part; and wherein the lead pin is electrically connected to the second terminal part while being disposed to the projection. a dispersive part for dispersing and reflecting light entering the package from the light entrance part; a light detection element for detecting the light dispersed and reflected by the dispersive part; a support for supporting the light detection element, such as to form a space between the dispersive part and the light detection element, characterized in that the support is a hollow structure that includes a base wall part, arranged so as to oppose the stem, having the light detection element secured thereto, and a side wall part, arranged so as to erect from a side of the dispersive part to the stem, for supporting the base wall part, and in that the spectrometer further comprises a lead pin penetrating through the stem, a projection projecting from the support, wherein the base wall part, side wall part, and projection are formed integrally; and a wiring including a first terminal part electrically connected to a terminal of the light detection element and a second terminal part arranged in the projection; wherein the projection is arranged at such a position as to be separated from the stem and to project from the side wall part to the side opposite from the dispersive part; and wherein the lead pin is electrically connected to the second terminal part while being disposed to the projection.