In controlling light condensing irradiation with laser light using a spatial light modulator, an incident pattern of the laser light and respective refractive indices of first and second propagation media on a propagation path are acquired, the number of light condensing points, and the light condensing position and the light condensing intensity at each light condensing point are set, an aberration condition caused by the first and second propagation media is derived, and by taking the aberration condition into account, a modulation pattern to be presented in the spatial light modulator is designed. Further, in designing the modulation pattern, a design method focusing on an effect of a phase value at one pixel is used, and in evaluating the light condensing state at the light condensing point, a propagation function that takes the aberration condition into account is employed.