The effect of antireflection (AR) coating on optical transparency for SiC membrane and the accelerated radiation damage of thicker AR film of 0.4 μm in thickness on a 2‐μm‐thick SiC membrane have been investigated in detail using SiO2, Al2O3, and ITO (indium tin oxide) films. SiO2, Al2O3, and ITO films were suitable for obtaining higher optical transparency and reducing the amplitude of interference fringes. The transmittance above 80% at 633 nm was achieved for 1‐μm‐thick as‐deposited SiC membrane with these AR films on both sides. AR films showed film stress change toward the compressive direction by synchrotron radiation (SR) irradiation. ITO film was found to have the strongest durability against SR irradiation among the AR films studied. The measured maximum and 3σ values forXandYcoordinates of the SR‐induced displacement of the SiC membrane with 0.4‐μm‐thick ITO film on one side were 30 nm andX=11 andY=39 nm, respectively, after irradiation of 191 kJ/cm2. Optical transparency of the mask membrane with ITO film was not changed after SR irradiation.