A structured illumination microscope includes a spatial light modulator containing ferroelectric liquid crystals, an interference optical system for illuminating a specimen with an interference fringe generated by making lights from the spatial light modulator interfere with each other, a controller for applying a voltage pattern having a predetermined voltage value distribution to the ferroelectric liquid crystals, an image forming optical system for forming an image of the specimen, which has been irradiated with the interference fringe, an imaging element for generating an image by imaging the image formed by the image forming optical system, and a demodulating part for generating a demodulated image using a plurality of images, wherein the controller applies an image generation voltage pattern for generating the demodulated images and a burn-in prevention voltage pattern calculated based on the image generation voltage pattern to the ferroelectric liquid crystals.