A laser surface treatment for reducing reflection loss on the surface of an optical material is provided. A metal film is formed on the surface of the optical material, and then the metal film is removed from the optical material by irradiation of an ultra-intense short-pulse laser beam having a pulse width of 1 femtosecond to 100 picoseconds, so that a fine periodic structure is formed on the surface of the optical material exposed by the removal of the metal film. The obtained fine periodic structure has asperities with a periodic interval of preferably 50 to 1000 nm, which can be controlled by changing the laser energy density.