PURPOSE: To prevent the leakage of a developer out of a developing apparatus provided in an image forming device.

CONSTITUTION: A developing apparatus body 20 forming the housing of a developing apparatus 6 is provided with a developing sleeve 26 pivoted so as to be rotatable. Two lines of developer splash preventive slots 30 are provided in the upper face portion 20b of the lower jaw portion 20a of the developing apparatus body 20 facing to the developing sleeve 26 lower periphery. A developer splashing by the rotation of the developing sleeve 26 is entrained into a spiral turbulent flow produced in the developer splash preventive slots 30 so as to prevent direct leakage outside the developing apparatus 6. Further a bottle neck 32 is formed between the periphery of a light-sensitive body drum 3 and a curved face 20c facing to the periphery so as to prevent the leakage of the developer.