A conveying device includes: a conveyor for conveying a sheet; a path defining member having a first conveying surface that guides the sheet; and a sensor device for sensing the sheet. The sensor device includes: a sensor casing provided on the path defining member and including a second conveying surface that guides the sheet and a main wall whose outer surface is exposed from the path defining member and contiguous to the first conveying surface; a movable member including (i) a contact portion projecting to a second-conveying-surface side of the main wall through an opening formed in the main wall and (ii) a sensed portion located in the sensor casing and moved by the sheet conveyed on the second conveying surface while contacting the contact portion; and a signal output device, provided in the sensor casing, for sensing the sensed portion to output a signal related to its position.