A developing agent including a toner particle obtained by using a dispersion containing a solvent, a granular mixed compound having a binder resin and a coloring agent dispersed in the solvent, and, as an additive to disperse a compound, a combination of a surfactant and a basic compound or a combination of a sulfone-based surfactant and a polycarboxylic acid-based surfactant, wherein the additive remaining in the developing agent is within a predetermine range.