An image reading apparatus comprising: a conveyance unit to convey a sheet; an illumination unit to irradiate the sheet that is conveyed by the conveyance unit with visible light and infrared light; an imaging unit to receive visible light and infrared light reflected from the sheet and to capture a visible image and an infrared image; an image processing unit configured to detect an edge of the sheet based on the captured infrared image and to correct the visible image based on the detected edge, and a background plate including infrared light low reflective parts that are provided in respective end portions of the background plate in a direction orthogonal to a conveyance direction of the sheet within an imaging range of the imaging unit so as to overlap at least a side edge portion of the sheet and that diffusely reflect visible light and reflect infrared light at a lower reflectance than the sheet, wherein the infrared light is absorbed by the infrared light low reflective parts, and a light diffusing and reflecting member that is provided in a central portion of the background plate in a direction orthogonal to a conveyance direction of the sheet excluding the low reflective parts, and that reflects visible light and infrared light, and the image processing unit corrects the visible image based on visible light reflected from the light diffusing and reflecting member and corrects the infrared image based on infrared light reflected from the light diffusing and reflecting member. a conveyance unit to convey a sheet; an illumination unit to irradiate the sheet that is conveyed by the conveyance unit with visible light and infrared light; an imaging unit to receive visible light and infrared light reflected from the sheet and to capture a visible image and an infrared image; an image processing unit configured to detect an edge of the sheet based on the captured infrared image and to correct the visible image based on the detected edge, and a background plate including infrared light low reflective parts that are provided in respective end portions of the background plate in a direction orthogonal to a conveyance direction of the sheet within an imaging range of the imaging unit so as to overlap at least a side edge portion of the sheet and that diffusely reflect visible light and reflect infrared light at a lower reflectance than the sheet, wherein the infrared light is absorbed by the infrared light low reflective parts, and a light diffusing and reflecting member that is provided in a central portion of the background plate in a direction orthogonal to a conveyance direction of the sheet excluding the low reflective parts, and that reflects visible light and infrared light, and the image processing unit corrects the visible image based on visible light reflected from the light diffusing and reflecting member and corrects the infrared image based on infrared light reflected from the light diffusing and reflecting member. infrared light low reflective parts that are provided in respective end portions of the background plate in a direction orthogonal to a conveyance direction of the sheet within an imaging range of the imaging unit so as to overlap at least a side edge portion of the sheet and that diffusely reflect visible light and reflect infrared light at a lower reflectance than the sheet, wherein the infrared light is absorbed by the infrared light low reflective parts, and a light diffusing and reflecting member that is provided in a central portion of the background plate in a direction orthogonal to a conveyance direction of the sheet excluding the low reflective parts, and that reflects visible light and infrared light, and the image processing unit corrects the visible image based on visible light reflected from the light diffusing and reflecting member and corrects the infrared image based on infrared light reflected from the light diffusing and reflecting member.