An optical scanning lens is for use in an optical scanning device in which a light beam forming a line image elongated in a direction corresponding to a main-scanning direction is deflected at a constant angular velocity by a deflector having a reflecting surface in a vicinity of a position of the line image, and in which a deflected beam is focused by the optical scanning lens to form a beam spot on a surface to be scanned so that a constant velocity optical scanning of the surface to be scanned is effected, the optical scanning lens having a single-lens construction and being constructed such that at least one of lens surfaces has an asymmetrical configuration with respect to an optical axis within a plane of deflection, the asymmetrical configuration with respect to the optical axis being designed so that a field curvature is properly corrected and a proper constant-velocity characteristic is obtained over an entire effective optical scanning area, and the plane of deflection being defined as a plane including the optical scanning lens and parallel to the direction corresponding to the main-scanning direction.