To solve problems that an improvement is desired even from environmental problems because a sheet or a formed product comprising a nonwoven fabric or a recycled paper consisting essentially of a conventional organic natural material is insufficient in shape stability including the strength or has problems in recyclability and safety and is not in a satisfactory state with the result that uses are limited and the recycling ratio of waste paper or materials recovered with much effort is low.

As a result of intensive studies made to solve various kinds of problems in quality or uses and to provide a method for shape stabilizing processing including the strength of the nonwoven fabric or recycled paper comprising the organic natural material gentle to global environments, it has been found out that the problems are solved by processing the nonwoven fabric or recycled paper according to a cross-linking reaction with a dihalogeno- monosubstituted-triazine-based compound having a water-soluble substituent group to provide the nonwoven fabric or recycled paper comprising especially the organic natural material excellent in strength.