An image scanning apparatus has a conveyer, a first scanning device configured to scan an image on one surface of an original sheet at a first scanning position, a second scanning device configured to scan an image on an other surface of the original sheet at a second scanning position. A controller is configured to execute a first adjustment process to adjust light amount adjustment of the first scanning device before scanning the original sheet subject to the received scanning instruction, start scanning after the first adjustment process, execute a determination process to determine, after starting conveying the original sheet, whether a light adjustment of the second scanning device is to be executed, execute a second adjustment process, when it is determined to start the light adjustment of the second scanning device, and stop conveying the original sheet when no original sheet is located at the first scanning position.