A laser beam scanning optical apparatus has a focusing lens having different optical powers in the main scanning direction and the sub-scanning direction, moving means for moving the focusing lens on an optical direction, detecting means for detecting a state of convergence of the laser beam on a scanned surface, and control means for adjusting the convergence position of the laser beam by moving the focusing lens via driving said moving means based on the detection result of the detection means. In the aforementioned construction, the state of the convergence of the laser beam on a scanned surface is adjusted in the main scanning direction and the sub-scan direction by moving the focusing lens in an optical axis. The focusing lens is moved to a position of optimum convergence based on the construction of the optical system by detecting the state of convergence in the main scan direction and the sub-scan direction via a detecting means.