A roughness evaluation method for evaluating a roughness of lines formed on a substrate includes a measuring step of irradiating light onto a plurality of locations of the substrate and measuring a state of reflected light by a scatterometry; and an analyzing step of evaluating the roughness of the lines based on a variation in value measured in the measuring step. A roughness evaluation system includes an optical device for irradiating light onto the substrate and measuring a state of reflected light by a scatterometry; a moving device for moving the substrate in at least one of an x-direction and a y-directions on a horizontal plane; a controller for controlling the moving device such that the optical device measures a plurality of locations on the substrate; and an analysis unit for evaluating the roughness based on a variation in measured values at the plurality of locations on the substrate.