PURPOSE: To prevent surely the scattering of a developer with a light press contact force and to obtain a sharp image, by bringing a sealing plate consisting of plural sheets of flexible films which are superposed to strip easily with deviation in forward end edges into press contact with the surface of a photoreceptor.

CONSTITUTION: Two sheets of flexible films 13, 14 are adhered on a base plate 12 of a flexible sealing plate 11 mounted on a guide plate 10 to prevent the scattering of a developer and is kept in light press contact with the surface of a photoreceptor 1. The forward ends of the films 13, 14 are superposed with about 1mm deviation from each other, and when said parts contact with the photoreceptor 1, a gap 16 is formed in the foward end parts. The scattering of the developer De is prevented by the film 13 and is then prevented positively by the film 14. As the photoreceptor 1 revolves, the developer is captured in the gap 16 in the evacuated state; therefore, the developer is prevented from scattering to the outside of the device. Since the plate 11 is kept in press contact lightly with the photoreceptor 1, the electrostatic latent image thereon is kept free from disturbance prior to development hence from contamination of image.