NOVELTY - The method involves forming an opening which penetrates a silicon oxide film and reaches an n-type impurity diffused layer (2) and forming an undercut region between a silicon oxide film (3) and a p-type single crystal silicon substrate (1a) by etching an impurity diffused layer by an aqueous alkali solution through an opening (4). A succeedingly anisotropic etching is performed to a silicon plane which is exposed by the aqueous alkali solution being dependent on a spatial breadth of the undercut region. The silicon oxide film is removed after the anisotropic etching.    USE - Manufacturing method of low reflection substrate such as p-type single crystal silicon substrate and n-type single crystal silicon substrate, of photovoltaic apparatus (claimed) such as single crystal silicon solar cell.    ADVANTAGE - Since an impurity diffused layer exists in the substrate surface directly under a silicon oxide film which is a protective film, when immersed in aqueous alkali solution, the undercut region formed in an impurity diffusion layer portion horizontally widens at high-speed. A texture shape is formed according to the horizontally wide speed of the undercut region. Thus etching time required in order to form a texture in the substrate whole surface uniformly can be shortened. Since anisotropic etching by an alkali is performed in the state protected by the formed silicon oxide film, the surface which becomes opposite can prevent the surface contamination by the uneven shaped formation and the alkali to a substrate back surface side which is not intended. The improvement of the characteristic at the time of this using the substrate for solar cell preparation can be achieved. The substrate back surface side can be etched by the alkali, so that the effect which prevents a completion substrate thickness becoming thin too much can be acquired.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for manufacturing method of photovoltaic apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional drawing explaining the process of the preparation process of the low reflection substrate.    P-type single crystal silicon substrate (1a)    N-type impurity diffused layer (2)    Silicon oxide film (3)    Opening (4)    Texture recessed portion (5)