The present invention provides a method for producing a three-dimensional product having a nanoporous surface in which the pore density, pore size or pore size distribution can be easily and readily controlled. The invention combines two techniques: a method for producing a three-dimensional product in which a yarn is knitted or woven to finish into an arbitrary three-dimensional shape, and a method for transforming a surface consisting of a material in which nanoparticles are dispersed in a matrix to a nanoporous surface by immersing the surface in a liquid which dissolves the nanoparticles but does not dissolve the matrix.