A range finding device comprising: a light projecting unit mounted on a moving body, having an irradiation domain extending in a horizontal direction, and configured to project intensity-modulated irradiation light; an image capturing unit mounted on the moving body, and configured to capture an image of an object irradiated with the irradiation light; a light projection controller configured to control an intensity of the irradiation light in accordance with a timing at which the image capturing unit captures the image; and a synchronous detection unit (14,15,18) configured to extract a region in which brightness changes in synchronism with intensity modulation of the irradiation light, as a synchronous detection region, from the image captured by the image capturing unit; characterized by an edge detector configured to detect an edge of the synchronous detection region; and a range calculator configured to calculate a distance to the object on the basis of the edge of the synchronous detection region detected by the edge detector, wherein if the change in the brightness of the image captured by the image capturing unit brings about a brightness output value in a non-linear region of the image capturing unit, the synchronous detection unit is configured to calculate an amplitude and a direct current component of the irradiation light which are needed to shift the change in the brightness of the image to a linear region of the image capturing unit, and the light projection controller is configured to control the intensity of the irradiation light on the basis of the calculated amplitude and direct current component of the irradiation light. a light projecting unit mounted on a moving body, having an irradiation domain extending in a horizontal direction, and configured to project intensity-modulated irradiation light; an image capturing unit mounted on the moving body, and configured to capture an image of an object irradiated with the irradiation light; a light projection controller configured to control an intensity of the irradiation light in accordance with a timing at which the image capturing unit captures the image; and a synchronous detection unit (14,15,18) configured to extract a region in which brightness changes in synchronism with intensity modulation of the irradiation light, as a synchronous detection region, from the image captured by the image capturing unit; characterized by an edge detector configured to detect an edge of the synchronous detection region; and a range calculator configured to calculate a distance to the object on the basis of the edge of the synchronous detection region detected by the edge detector, wherein if the change in the brightness of the image captured by the image capturing unit brings about a brightness output value in a non-linear region of the image capturing unit, the synchronous detection unit is configured to calculate an amplitude and a direct current component of the irradiation light which are needed to shift the change in the brightness of the image to a linear region of the image capturing unit, and the light projection controller is configured to control the intensity of the irradiation light on the basis of the calculated amplitude and direct current component of the irradiation light.