A spectrometric measurement apparatus comprising: a light radiation unit configured to radiate light onto an image carrying medium ; a hole array including plural openings that are arranged in a one-dimensional manner for transmitting a part of the light corresponding to diffusion light from the image carrying medium; an imaging optical system configured to focus an image from the hole array; a diffraction element configured to diffract the light for focusing the image; and a light receiving unit including plural pixels arranged in a one-dimensional manner configured to receive the light that has been dispersed by the diffraction element, the light receiving unit further including plural spectrometric sensors each corresponding to a predetermined number of the plural pixels, wherein the light transmitted through each of the plural openings of the hole array is dispersed by the diffraction element, and then the light enters the plural pixels corresponding to one of the plural spectrometric sensors of the light receiving unit so that spectral properties of the diffusion light are acquired, and characterised in that a structure of the diffraction element includes variations that are formed in accordance with an image height of the image that is focused by the imaging optical system, wherein the image height of an image is a distance a x (λ) along the light receiving unit with respect to an origin corresponding to the center of the light axis of the imaging optical system at which the image is focused on the light receiving unit by the imaging optical system, wherein periods of the diffraction element are varied such that a positional difference along the light receiving unit between a x at a first wavelength of light for focusing the image and a x at a second wavelength of light for focusing the image is within a predetermined range, wherein a x is a distance along the light receiving unit with respect to an origin of zero order light. a light radiation unit configured to radiate light onto an image carrying medium ; a hole array including plural openings that are arranged in a one-dimensional manner for transmitting a part of the light corresponding to diffusion light from the image carrying medium; an imaging optical system configured to focus an image from the hole array; a diffraction element configured to diffract the light for focusing the image; and a light receiving unit including plural pixels arranged in a one-dimensional manner configured to receive the light that has been dispersed by the diffraction element, the light receiving unit further including plural spectrometric sensors each corresponding to a predetermined number of the plural pixels, wherein the light transmitted through each of the plural openings of the hole array is dispersed by the diffraction element, and then the light enters the plural pixels corresponding to one of the plural spectrometric sensors of the light receiving unit so that spectral properties of the diffusion light are acquired, and characterised in that a structure of the diffraction element includes variations that are formed in accordance with an image height of the image that is focused by the imaging optical system, wherein the image height of an image is a distance a x (λ) along the light receiving unit with respect to an origin corresponding to the center of the light axis of the imaging optical system at which the image is focused on the light receiving unit by the imaging optical system, wherein periods of the diffraction element are varied such that a positional difference along the light receiving unit between a x at a first wavelength of light for focusing the image and a x at a second wavelength of light for focusing the image is within a predetermined range, wherein a x is a distance along the light receiving unit with respect to an origin of zero order light. <EOS>