A light source irradiates the measuring object with slit light having a width in an X direction. An image sensor receives reflected light from the measuring object, has a plurality of pixels two-dimensionally arranged in a U direction corresponding to the X direction and a V direction corresponding to a Z direction, and outputs a light receiving amount of the reflected light. A detecting unit detects a position of a pixel in the V direction. A generating unit generates a profile of the X-Z cross section from each position of the plurality of pixel rows in the U direction and the peak position in the V direction. A resolution in the V direction of the image sensor is lower than a resolution in the U direction of the image sensor.