The surface roughness of spaghetti is an important factor influencing noodle quality during and after cooking. In this study, we describe a novel, rapid, and low-cost method, based on the principal that an object with a rougher surface refracts more light, to measure the surface roughness of spaghetti using images acquired with a common digital camera. This method helps determine the surface roughness using gray-level frequency distributions from transmission images and facilitates the measurement of surface geometry to the same accuracy as that of traditional, high-performance laser-scanning microscopy techniques. Furthermore, this method enables rapid measurement of the entire surface geometry of the spaghetti, including the steeply sloped and shaded regions, which are difficult to measure by the conventional laser method, owing to lower reflectance or shielding of the laser beam.