The present application discloses image generation device for generating sample image representing sample. The image generation device includes laser source portion which emits laser beam, convertor for converting laser beam into multiplexed beam, in which reflected beam after reflection of laser beam by sample and reference beam after modulation of phase of the laser beam are multiplexed, first signal generator which generates first detection signal corresponding to light quantity of multiplexed beam, image generator which generates sample image, and modulator which modulates the phase to cause periodic variation of light quantity of multiplexed beam. The first detection signal includes signal component representing change from increase to decrease in the periodic variation. The image generator uses signal component to generate sample image.