A method for manufacturing a concave diffraction grating, the concave diffraction grating including: a reflection film including a plurality of grating grooves; a holding film formed of metal and having one surface provided with the reflection film; a concave substrate including a concave surface; and an affixing layer that is provided between the concave surface and the other surface of the holding film and affixes the holding film and the reflection film to the concave substrate, the holding film having a linear expansion coefficient with which a shape of the holding film changes in the same manner as the reflection film due to a temperature change, the method comprising: forming grating grooves on a planar substrate; forming the reflection film on the grating grooves of the planar substrate; forming the holding film on the reflection film; producing a planar diffraction grating in which the grating grooves are formed in the reflection film by peeling the planar substrate from a stacked body of the reflection film and the holding film; disposing the affixing layer on an opposite surface of the planar diffraction grating from the surface provided with the grating grooves and disposing the concave substrate to face the surface of the planar diffraction grating on which the affixing layer is disposed; and deforming a shape of the planar diffraction grating to follow a shape of the concave surface of the concave substrate to form the concave diffraction grating. the concave diffraction grating including: a reflection film including a plurality of grating grooves; a holding film formed of metal and having one surface provided with the reflection film; a concave substrate including a concave surface; and an affixing layer that is provided between the concave surface and the other surface of the holding film and affixes the holding film and the reflection film to the concave substrate, the holding film having a linear expansion coefficient with which a shape of the holding film changes in the same manner as the reflection film due to a temperature change, a reflection film including a plurality of grating grooves; a holding film formed of metal and having one surface provided with the reflection film; a concave substrate including a concave surface; and an affixing layer that is provided between the concave surface and the other surface of the holding film and affixes the holding film and the reflection film to the concave substrate, the holding film having a linear expansion coefficient with which a shape of the holding film changes in the same manner as the reflection film due to a temperature change, the method comprising: forming grating grooves on a planar substrate; forming the reflection film on the grating grooves of the planar substrate; forming the holding film on the reflection film; producing a planar diffraction grating in which the grating grooves are formed in the reflection film by peeling the planar substrate from a stacked body of the reflection film and the holding film; disposing the affixing layer on an opposite surface of the planar diffraction grating from the surface provided with the grating grooves and disposing the concave substrate to face the surface of the planar diffraction grating on which the affixing layer is disposed; and deforming a shape of the planar diffraction grating to follow a shape of the concave surface of the concave substrate to form the concave diffraction grating. forming grating grooves on a planar substrate; forming the reflection film on the grating grooves of the planar substrate; forming the holding film on the reflection film; producing a planar diffraction grating in which the grating grooves are formed in the reflection film by peeling the planar substrate from a stacked body of the reflection film and the holding film; disposing the affixing layer on an opposite surface of the planar diffraction grating from the surface provided with the grating grooves and disposing the concave substrate to face the surface of the planar diffraction grating on which the affixing layer is disposed; and deforming a shape of the planar diffraction grating to follow a shape of the concave surface of the concave substrate to form the concave diffraction grating.