PURPOSE: To obtain an aramid fiber for reinforcing cement, having good collecting property and excellent in dispersibility in cement by applying a specific amount of a treating agent containing a specific water-soluble polyester, etc., to the surface of aramid fiber.

CONSTITUTION: A treating agent obtained by mixing (A) 60-85wt.% of a water- soluble copolyester obtained by copolymerizing an aromatic dicarboxylic acid, an alkylene glycol, a dicarboxylic acid having SO3M (M is a metal) and/or a polyoxyalkylene glycol with (B) 10-30wt.% of wax having 50-110°C point as wax jointly used with the component A and further, (C) 5-10wt.% of polysiloxane having 3-100cst viscosity at 25°C and preparing the mixture in an emulsion is applied in an amount of 10-30wt.% based on fiber weight to the surface of an aramid fiber in a drawing process of the fiber to provide the objective aramid fiber having good collecting property in cutting into a short fiber and excellent in handleability in processing process and dispersibility in a cement matrix and reinforcing effect.