A laser processing device for performing laser processing on an object to be processed by applying laser light of a first wavelength from a first surface side of the object to be processed to the object to be processed, the laser processing device comprising: a laser light source configured to output the laser light; a converging unit configured to converge the laser light toward the first surface to form a converging point; a camera configured to image reflected light of the laser light from the first surface; a spatial light modulator configured to modulate the laser light according to a modulation pattern; a support table configured to support the object to be processed; the laser processing device being characterised by the following: a moving mechanism for moving the support table; a converging lens for converging the reflected light toward the camera; and a controller configured to execute acquisition processing of applying the laser light to the first surface by controlling the laser light source and imaging the reflected light by controlling the camera to acquire a reflectance of the first surface with respect to the first wavelength, wherein before executing the acquisition processing, the controller executes modulation processing of causing the spatial light modulator to present the modulation pattern for lowering a power density of the laser light on the first surface, wherein as the modulation processing, the controller causes the spatial light modulator to present a shift pattern as the modulation pattern for shifting the converging point from the first surface, and wherein the controller moves the support table by the moving mechanism so that the reflected light from the first surface is converged to the camera when the converging point is shifted from the first surface. a laser light source configured to output the laser light; a converging unit configured to converge the laser light toward the first surface to form a converging point; a camera configured to image reflected light of the laser light from the first surface; a spatial light modulator configured to modulate the laser light according to a modulation pattern; a support table configured to support the object to be processed; the laser processing device being characterised by the following: a moving mechanism for moving the support table; a converging lens for converging the reflected light toward the camera; and a controller configured to execute acquisition processing of applying the laser light to the first surface by controlling the laser light source and imaging the reflected light by controlling the camera to acquire a reflectance of the first surface with respect to the first wavelength, wherein before executing the acquisition processing, the controller executes modulation processing of causing the spatial light modulator to present the modulation pattern for lowering a power density of the laser light on the first surface, wherein as the modulation processing, the controller causes the spatial light modulator to present a shift pattern as the modulation pattern for shifting the converging point from the first surface, and wherein the controller moves the support table by the moving mechanism so that the reflected light from the first surface is converged to the camera when the converging point is shifted from the first surface. a moving mechanism for moving the support table; a converging lens for converging the reflected light toward the camera; and a controller configured to execute acquisition processing of applying the laser light to the first surface by controlling the laser light source and imaging the reflected light by controlling the camera to acquire a reflectance of the first surface with respect to the first wavelength, wherein before executing the acquisition processing, the controller executes modulation processing of causing the spatial light modulator to present the modulation pattern for lowering a power density of the laser light on the first surface, wherein as the modulation processing, the controller causes the spatial light modulator to present a shift pattern as the modulation pattern for shifting the converging point from the first surface, and wherein the controller moves the support table by the moving mechanism so that the reflected light from the first surface is converged to the camera when the converging point is shifted from the first surface.