An optical scanner emits a light beam in accordance with an image forming signal and deflects the light beam in a first direction. A scanned face is adapted to be scanned by the deflected light beam to form a scanning line while being moved in a second direction perpendicular to the first direction, thereby forming a latent image thereon. A virtual scanned face is defined as a plane including the scanning line and orthogonal to an optical axis of the optical scanner. The shape of a beam spot formed by the light beam incident on the virtual scanned face is approximated to an ellipse. The scanned face is inclined from the virtual scanned face so as to rotate about the scanning line, in accordance with an inclined angle of an major axis of the ellipse from the second direction on the virtual scanned face.