The charge control agent comprises aggregate particles including an azo-type iron complex salt represented by the following chemical formula [VI] ##STR00001## (in the chemical formula [VI], B.sup.+ is (H.sup.+).sub.x(Na.sup.+) .sub.1-x and x is mole ratio and 0.6 to 0.9, or B.sup.+ is (H.sup.+).sub.y(Na.sup.+).sub.1-y and y is mole ratio and 0 to 0.2) and the aggregate particles have 0.5 to 5.0 microns of an average particle size. A toner for developing an electrostatic image comprises a resin for the toner and the charge control agent. An image formation process of electrophotography comprises a step for developing an electrostatic latent image on an electrostatic latent image frame by a developer including the toner.