Abstract: This invention describes a method of manufacturing silica waveguide optical components in which silica glass films are laminated on a substrate by repeating a unit operation in which a sol material, a precursor of glass particles, is coated and then the coated layer is heated in an oxygen atmosphere. wherein the heating temperature is controlled in such a manner that the radius of curvature of warping of the substrate is 2 m or more after the coated layer is heated, thereby preventing cracking in the formed silica glass film and/or peeling of the coated layer. At locations where a difference in height is present, at least when sol is coated first time, the thickness of the coated layer is less than that of one of the subsequent coated layers.