An optical scanning apparatus comprising: a light source configured to emit a light beam; scanning means configured to deflect the light beam from the light source so that the light beam scans a photosensitive member; an optical lens configured to guide the light beam deflected by the scanning means onto the photosensitive member; and a lens supporting member configured to support the optical lens and to which one end of the optical lens in a longitudinal direction is fixed such that the one end of the optical lens is stationary with respect to the lens supporting member characterized in that the lens supporting member includes a movable supporting portion to which another end of the optical lens in the longitudinal direction is fixed such that said another end of the optical lens is stationary with respect to the movable supporting portion; the lens supporting member further includes a light beam passing hole to allow a scanned light beam to pass through, and includes an opening to connect to the light beam passing hole, wherein the movable supporting portion is fitted into the opening which is arranged to restrict movement of the movable supporting portion in a direction (z) perpendicular to the longitudinal direction (x) and an optical axis (y) of the optical lens which is perpendicular to the longitudinal direction (x), and wherein the movable supporting portion fitted in the opening is movable in the longitudinal direction (x) by the movable supporting portion sliding in the opening in the longitudinal direction (x). a light source configured to emit a light beam; scanning means configured to deflect the light beam from the light source so that the light beam scans a photosensitive member; an optical lens configured to guide the light beam deflected by the scanning means onto the photosensitive member; and a lens supporting member configured to support the optical lens and to which one end of the optical lens in a longitudinal direction is fixed such that the one end of the optical lens is stationary with respect to the lens supporting member characterized in that the lens supporting member includes a movable supporting portion to which another end of the optical lens in the longitudinal direction is fixed such that said another end of the optical lens is stationary with respect to the movable supporting portion; the lens supporting member further includes a light beam passing hole to allow a scanned light beam to pass through, and includes an opening to connect to the light beam passing hole, wherein the movable supporting portion is fitted into the opening which is arranged to restrict movement of the movable supporting portion in a direction (z) perpendicular to the longitudinal direction (x) and an optical axis (y) of the optical lens which is perpendicular to the longitudinal direction (x), and wherein the movable supporting portion fitted in the opening is movable in the longitudinal direction (x) by the movable supporting portion sliding in the opening in the longitudinal direction (x). characterized in that the lens supporting member includes a movable supporting portion to which another end of the optical lens in the longitudinal direction is fixed such that said another end of the optical lens is stationary with respect to the movable supporting portion; the lens supporting member further includes a light beam passing hole to allow a scanned light beam to pass through, and includes an opening to connect to the light beam passing hole, wherein the movable supporting portion is fitted into the opening which is arranged to restrict movement of the movable supporting portion in a direction (z) perpendicular to the longitudinal direction (x) and an optical axis (y) of the optical lens which is perpendicular to the longitudinal direction (x), and wherein the movable supporting portion fitted in the opening is movable in the longitudinal direction (x) by the movable supporting portion sliding in the opening in the longitudinal direction (x).