A developing device and an image forming apparatus having the same include a frame having a knob part, a photosensitive body provided in front of the knob part with respect to a first direction of mounting the developing device, and a rotation guide part provided in front of the photosensitive body with respect to the first direction, and to guide a rotational motion of the developing device. When the developing device is removed from the image forming apparatus, the knob part is rotated upward. A first protrusion is provided on a side surface of the frame to determine a mounting position of the developing device. When the knob part is rotated upward, the first protrusion is rotated in the same direction as the knob part. Accordingly, the developing device has an improved mounting/removing structure adequate to compactly manufacture the image forming apparatus, and improves handling convenience in mounting and removing the developing device.