A foldable dot sight device is provided that includes a body capable of being assembled into a firearm. A dot generator is disposed on the body, and is capable of generating a dot for aiming at a target. A reflective mirror is provided, which transmits an image of a target toward the user and reflects the dot generated by the dot generator. A housing is connected to the reflective mirror. A protective cover includes a sliding guide rotatably connected to the body and rotates the housing in a folding or unfolding direction according to a rotational position.