An etchant for chalcogenide glass or oxychalcogenide glass contains an acid and a compound, e.g., an oxidizing agent, which reacts with hydrogen chalcogen to guarantee safe etching of sulfuric glasses in rendering the glass surface smooth and free from surface defects. The etchant is used for an etching method in which a member made of chalcogenide glass or oxychalcogenide glass is dipped in the prepared etchant. The member can make a glass optical member having a surface, substantially free from latent scratch, whose surface roughness difference is one micron meter or less in a length of 0.1 micron meter taken along the surface.