An optical module includes: a measuring device including a measuring portion that measures light reflected at a measurement position of a measurement target, a light source that radiates light onto the measurement position in a direction crossing a measurement optical axis oriented from the measurement position to the measuring portion, and a window through which light incident on the measuring portion passes; and a shutter that opens and closes the window of the measuring device. The shutter is provided with a reference object disposed closer to the measuring portion side than the measurement position on the measurement optical axis, on a face of the shutter facing the measuring portion when closing the window, and the optical module includes a light guide that guides the light from the light source to the reference object when the window is closed by the shutter.