An optical scanning system includes a variable-focus element, an imaging lens and a deflector, wherein the reciprocal of the focal length f of the variable-focus element is changed from 1/fMIN to 1/fMAX, and for the case that the equation 1/f={(1/fMAX)+(1/fMIN)}/2 holds, a beam which has passed through the variable-focus element is a divergent beam, and x 2 + x 2 2 x 1 > x 3 ( 1 ) is satisfied, where x1 represents a distance from a virtual image point of the divergent beam to the principal point on the entry side of the variable-focus element, x2 represents a distance from the principal point on the exit side of the variable-focus element to the principal point on the entry side of the imaging lens, and x3 represents a distance from the principal point on the exit side of the imaging lens to an image point.