Light beam scanning device suppressing thermal deformation of a scanning lens and image forming device

An image forming device forming a latent image on a photoreceptor through scanning the photoreceptor by using a light beam from a light beam scanning unit and developing the latent image, wherein

• the light beam scanning unit is a light beam scanning device deflecting, by using a rotating polygon mirror, a light beam emitted from a light source and condensing, by using a scanning lens, the deflected light beam onto a scanned surface, the light beam scanning device comprising:
• a base made of a metal or a resin;
• a motor unit attached to the base and rotating the polygon mirror;
• a holding member holding the scanning lens;
• and
• a fixing member disposed on a main surface of the base between the base and the holding member and having a longitudinal axis perpendicular to the main surface of the base, the fixing member fixing the holding member to the base with the holding member spaced away from the main surface of the base, wherein
• the base has, between the fixing member and the motor unit, a penetrating hole or groove around which heat transmitted from the motor unit through the base to the fixing member passes, wherein the penetrating hole or groove has a length greater than a width, and the penetrating hole or groove is intersected at a center thereof along the length by a plane passing through a rotational axis of the motor unit and the longitudinal axis of the at least one fixing member.