In an original reading apparatus, a conveying mechanism and a reading device start a conveying operation and a reading operation to acquire a read image when a detecting device detects an existence of an original. The read image is acquired in a first direction and has a prescribed width in a second direction orthogonal to the first direction. The first direction corresponds to a conveying direction of the original. A control device determines whether or not the read image includes an overall solid region with a single color. The overall solid region has: a length in the first direction longer than or equal to a prescribed length; and a width in the second direction equal to the prescribed width. When the read image includes the overall solid region, the control device outputs a signal indicative of incorrect detection of the existence of the original due to external light.