An electrophotography developing apparatus has been developed which can protect a developer holder and a layer thickness control member from damage. The device also prevents internal scattering of the developer while preventing a surplus supply of the developer to both ends on the peripheral surface of the developer holder. The unique advantages of the invention are derived through the utilization of sealing members having different elastic properties, which assume both bulk removal of excess developer while providing the needed uniform developer thickness. Another embodiment of the invention has the width of the layer thickness control member in a longitudinal direction set wider than the width of the developer holder in a longitudinal direction, and both side edges of the layer thickness control member are positioned outside both side edges of the developer holder. Proper sealing is assured by having the inner side edges of the sealing member positioned inside the side edges of the developer holder and outside the side edges of the image area of the image holder.