Method of processing a solid surface by gas cluster ion beam

For machining of a solid surface to prevent deformation of the corner portions of the concave-convex structure. Cluster protection layer is an uneven structure and cluster protection layer formation process of forming a solid surface consisting of a concave convex portion and the cluster protection layer coated form is not coated form, uneven structure is formed in the cluster protection layer formation process at the top an irradiation step of irradiating the gas cluster ion beam onto the solid surface, a method of processing a solid surface by gas cluster ion beam and a removal step of removing the cluster protection layer. The dose of the gas cluster ion beam n, when the etching efficiency of the cluster protection layer as an etching volume Y per cluster (provided that a and b are constants), the thickness T of the cluster protection layer, Meet.