A structure for mounting a screen grid member of a corona charger in an imaging device with a predetermined positional relation to the surface of a photoconductive member. The corona charger and the photoconductive member are mounted on a support base member. The support base member is provided with a mount opening where a substantially inverted U-shaped screen grid member carrying the screen grid is inserted. First locking lugs project from the inner wall surfaces of the mount opening, each of the first locking lugs having a surface opposite to a surface facing toward the photoconductive member formed as a locking surface substantially normal to the inner wall surface. Second locking lugs project from the inner wall surfaces of the mount opening, each of the second locking lugs having a surface facing the photoconductive member, formed as a locking surface substantially normal to the inner wall surface. Locking holes are defined on the screen grid member at the positions corresponding to the first locking lugs and the second locking lugs, respectively. The screen grid member is inserted into the mount opening and fixed thereto through engagements of the locking holes with the locking lugs.