An optical-writing-head positioner includes a spacer disposed between a latent image bearer to bear a latent image and an optical writing head to expose the latent image bearer to light to form a latent image on a surface of the latent image bearer. The spacer positions the optical writing head with respect to the latent image bearer. The spacer includes plural contact faces with the latent image bearer in an axial direction of the latent image bearer. The plural contact faces include a contact face having an arc with a radius of curvature equal to or less than a radius of the latent image bearer and one of the a contact face having an arc with a radius of curvature greater than the radius of the latent image bearer and a flat contact face to contact the surface of the latent image bearer.