The formation of nap-type structures induced by UV-laser irradiation of renatured gelatin films with various triple helix contents was observed by an atomic force microscope. Surface topography was found to be dependent on degree of helix content (DHC), fluence, and number of applied pulses (PN). The surface roughness (R-a) increased with PN following a hyperbolic curve for the renatured gelatin films with DHC of more than ca. 7%. The increment of R-a tended to be depressed with increasing DHC.