A method for modifying the surface of a substrate includes the following steps: (1) a step for forming a polysilazane coating by applying a polysilazane onto the surface of a substrate; (2) a step for applying an organic compound of which main backbone comprises an organic group represented by the following formula [1]: —[(R)mO]n— (wherein R represents an alkylene group, and m and n respectively represent a positive number of not less than 1) onto the surface of the polysilazane coating; and (3) a step for heating the substrate having undergone the steps (1) and (2), thereby converting the polysilazane to silica and bonding the organic compound to the silica of the silica layer.