An image acquisition device includes a light source, a spatial light modulator having a plurality of pixels two-dimensionally arranged and fro modulating a phase of excitation light output from the light source for each of the plurality of pixels, a first objective lens, a second objective lens, a photodetector, and a control unit for controlling an amount of phase modulation for each of the plurality of pixels in accordance with a two-dimensional phase pattern corresponding to the plurality of pixels. The phase pattern is generated based on a predetermined basic phase pattern. The basic phase pattern includes a first region in which the phase value continuously increases in a predetermined direction and a second region in which the phase value continuously decreases in the direction and facing the first region in the direction.