Abstract: The present disclosure relates to a ball and a valve seat for a fuel injector, in which an SiO-DLC functional layer having low friction properties is formed as an outermost layer in order to reduce a friction coefficient, a Mo-based material is applied to a bonding layer and a supporting layer for bonding the SiO-DLC functional layer to a base material and supporting the same to improve the heat resistance thereof, and only Mo particles of a pure ion state are deposited so as to form the bonding layer and the support layer, such that adhesive force and bonding force are increased to thus improve durability; and to a method for coating the same.