Abstract: A staining preventive treatment process for polyamide fiber which comprises the application of the compound of general formula I below and the compound of general formula II below to the polyamide fiber: ##STR1## in which R independently represents ##STR2## X independently represents hydrogen or alkali metal, and 1 is a number from 3 to 20, provided that 50-70% of R is ##STR3## and the remainder is at least one group selected from --OX, ##STR4## in which A represents ##STR5## X independently represents hydrogen or alkali metal, m is an integer from 2 to 6, and n is 0, 1, or 2.Staining by natural or artificial coloring agents is effectively prevented.