A photo film cassette includes a spool core, on which the photo film is wound in a form of roll. A cassette shell contains the spool core in rotatable fashion. First and second flanges are respectively secured to ends of the spool core, for regulating positions of sides of the photo film roll. A first ring-like lip is formed integrally with a periphery of the first flange, is projected toward the roll, is contacted on one edge of an outermost turn of the roll, and prevent the roll from being loosened. The first and second flanges are formed from resin in accordance with injection molding. The resin has temperature of thermal deformation being 80° C. or higher under 18.6 kg/cm2, modulus in elasticity in flexure being 13,000-30,000 kg/cm2, surface hardness being 80 or more in Rockwell R-scale, and high fluidity in molds for the injection molding. The first and second flanges have an outer diameter of 15 mm or more, thickness of 0.3 mm or less, and a maximum projected area of 100 mm2 or more as measured with a contour thereof kept substantially circular.