A measuring device a measurement unit configured to measure an image on a sheet, the measurement unit including a light emitting portion configured to illuminate the sheet with light, and a detecting portion configured to detect light reflected by the sheet; a supporting unit supporting the measurement unit; and a driving unit configured to move the measurement unit supported by the supporting unit in a scanning direction. A size, in the scanning direction, of a detectable range of the detecting portion in which the detecting portion is capable of detecting the reflected light from the sheet is larger than a size, in a sub-scanning direction perpendicular to the scanning direction and a normal direction of a surface of the sheet, of the detectable range of the detecting portion.