A conveying mechanism is disposed inside a housing of an image scanning device and is configured to convey the sheet along a common path to the scanning position in a first direction, and to convey the sheet having passed the scanning position selectively along a return path in a second direction and along a one-way path in the first direction. A scanning unit disposed inside the housing scans, at the scanning position, an image of a sheet. The discharge cover is openably and closably disposed in the housing and is configured, when open relative to the housing, to define a discharge port and receive the sheet conveyed along the one-way path and discharged through the discharge port. The maintenance cover is openably and closably disposed in the housing and is configured, when open relative to the housing, to expose the one-way path and the return path.