An image forming device includes a main frame having a body and a photoconductive drum which is provided removably in the main frame. An optical writing head is provided which is positioned relatively with respect to the photoconductive drum and includes a lens array at an output side of the optical writing head. A housing of a photoconductive drum unit is provided which rotatably supports the photoconductive drum and is positioned and supported on the body of the main frame. By contacting the lens array directly against a surface of the housing of the photoconductive drum unit, the optical writing head is positioned relatively with respect to the photoconductive drum. A shock absorbing member is provided between the lens array and a contact part where the lens array makes contact with the surface of the housing of the photoconductive drum unit.