To adjust the shape of an illumination light source easily to a required shape.
The method for adjusting a light source includes a step 102 for setting image modulation parameters Zj representing change in the actual shape for the target shape of an illumination light source, steps 113, 114 for determining a conversion matrix B of the image modulation parameters Zj and illumination system modulation parameters fBj with respect to a first illumination optical system where the shape of an illumination light source is adjusted based on the illumination system modulation parameters fBj, and a step 116 for determining a second set of values fBVj of an illumination system modulation parameters fBj corresponding to a first set of values ZVj of the image modulation parameters Zj by using the matrix B.