[Problem]To obtain a 
fiber-treating agent and 
polyester staple fibers having excellent processability during the 
processing of 
polyester staple fibers with high-pressure water-jets, and excellent 
nonwoven fabric hydrophilicity after the high-pressure water-jet process. [Means of Solution]The present invention provides a 
fiber-treating agent comprising a component A, which is a 
polyester compound produced by carrying out a condensation 
polymerization of an alkylene glycol, a polyalkylene glycol, and at least one member selected from the group consisting of aromatic dicarboxylic acids, C4-22 aliphatic dicarboxylic acids, and their ester-forming derivatives; a component B, which is a polyester compound produced by carrying out a condensation 
polymerization of a polyoxyalkylene monol, an alkylene glycol, and at least one member selected from the group consisting of aromatic dicarboxylic acids and their ester-forming derivatives; and a component C, which is a C4-6 
alkyl phosphate salt; and is characterized by components A, B, and C being blended in specific ratios. Also provided are polyester staple fibers treated with the treating agent, and a 
nonwoven fabric manufactured by 
processing the polyester staple fibers with high-pressure water jets.