A developing unit and an electro-photographic image forming apparatus having the same are provid. The developing unit includes a housing and a photosensitive medium, which has an end exposed to the outer side of the housing and that is rotatably mounted on the housing. A photosensitive medium shutter shields the exposed part of the photosensitive medium when a door is opened and exposes the exposed part of the photosensitive medium to the outside when the door is closed. The photosensitive medium shutter includes a first shielding plate that is moved between a first location where the exposed part is shielded and a second location where the exposed part is exposed to the outside of the housing. A second shielding plate is spread at the first location with respect to the first shielding plate and is overlapped with the first shielding plate at the second location.