A document conveying device includes a cover, a rigid stopper, and a biasing member. The cover includes a first cover plate and a second cover plate. The stopper is rigid, has a fixed end rotatably connected to the cover and a movable end moving in an elongated hole formed in the device main body accordance with a turning of the cover, and supports the cover in a fully opened posture when the movable end is locked to one end of the elongated hole. The biasing member moves the movable end of the stopper to a position P separated by a predetermined distance from the one end of the elongated hole.